Records of this parliament fortuitously still exist (they often don't), and can be read in Rotuli Parliamentorum in the original French and Latin, and in The Parliament Rolls Of Medieval England (PROME), in the original and English translation. It was, needless to say, an extremely eventful parliament. Proceedings began with the judgement on Roger Mortimer, who was bound and gagged and thus forcibly prevented from speaking in his own defence. Fourteen charges against him were read out. The first reveals Edward III's anger that Roger "usurped by himself royal power and the government of the realm concerning the estate of the king" when he had never been elected to the king's regency council, and states that Roger had filled the king's household and other positions of influence with his followers, and told men like John Wyard to spy on Edward, with the result that "our said lord the king was surrounded by his enemies so that he was unable to do as he wished, so that he was like a man living in custody." The second charge concerned Edward II, that "whereas the father of our lord the king was at Kenilworth by the ordinance and assent of the peers of the realm, to remain there at their pleasure in order to be looked after as was appropriate for such a lord, the said Roger by the royal power usurped by him, was not satisfied until he had him at his will, and ordained that he be sent to Berkeley Castle where he was traitorously, feloniously and falsely murdered and killed by him and his followers."
There was no other possible outcome, once these and the other dozen charges had been read out: Roger's guilt was deemed to be 'notorious' and he was condemned to be drawn and hanged, which sentence was carried out at Tyburn on 29 November. Then came his ally Sir Simon Bereford, a rather mysterious character accused and convicted of being a "helper and supporter of the said Roger de Mortimer in all his treasons, felonies and evil acts...which things are an encroachment on royal power, the murder of a liege lord, and the destruction of the royal blood line; and that he was also guilty of various other felonies and robberies, and the chief maintainer of robbers and felons." Bereford was also sentenced to death for these crimes, and executed on 24 December. Presumably Edward III had strong evidence of Bereford's guilt, though his involvement in the regime of 1327 to 1330 and his role in the presumed death of Edward II remain obscure.
Sir John Maltravers of Dorset, who with his brother-in-law Thomas, Lord Berkeley had been custodian of the former Edward II at Berkeley Castle in 1327, was sentenced to death in absentia because he had "principally, traitorously and falsely plotted the death" of Edward II's half-brother Edmund of Woodstock, earl of Kent, executed on 19 March 1330. "...[S]ince he knew of the death of King Edward, nevertheless the said John by ingenious means and by his false and evil subtleties led the said earl to understand the king was alive, which false plotting was the cause of the death of the said earl and of all the evil which followed." It is important to note here that although some contemporary chroniclers - even Adam Murimuth, who's normally pretty well-informed - thought that Maltravers was accused and convicted of the murder of Edward II, he was not, neither in 1330 nor at any other point in his very long life ( he was eventually allowed to return to England and lived until 1364). 1000 marks was offered as a reward if Maltravers was taken alive, and £50 for his head.
The fabulously-named Sir Bogo de Bayouse, a Yorkshire knight, and John Deveril were also sentenced to death in absentia for their role in entrapping the earl of Kent, and a price put on their heads. Both men had been at Corfe Castle in Dorset, where the earl of Kent and others thought Edward of Caernarfon was being held, in 1330; Kent admitted at his trial that he had given a letter intended for Edward to Deveril, who betrayed him and took it instead to Roger Mortimer. Deveril was thought to be hiding in the Dorset/Somerset/Wiltshire area in August 1331 (Patent Rolls 1330-34, p. 201), though he was never found and his fate is unknown. Somewhat ironically, one of the men ordered to search for and arrest him was 'John Mautravers the elder', father of the John Maltravers above. Sir Bogo de Bayouse fled to France and ultimately, with his wife Alice, to Italy, and died in Rome on 26 July 1334 (Seymour Phillips, Edward II, 2010, p. 576).
Two men, a knight of Somerset named Sir Thomas Gurney and a man-at-arms called William Ockley or Ogle, were also sentenced to death in absentia, "for the death of King Edward, the father of our present lord the king, that they falsely and traitorously murdered him." I've sometimes seen it stated that the supposed red-hot poker method of Edward II's murder was officially given out at this parliament as the cause of death. This is absolutely untrue. All that was stated about Gurney and Ockley's supposed murder of Edward is what I have quoted here. The cause of Edward II's death was never given in any official government source, and all we have is speculation and gossip by chroniclers. William Ockley disappeared and was never heard of again. Sir Thomas Gurney's subsequent fate is, by contrast, well-known, and I've written a long post about him and Ockley here.
Edward II's first cousin Henry, earl of Lancaster, and his adherents were pardoned for taking part in a failed rebellion against Queen Isabella and Roger Mortimer in late 1328/early 1329, and the many adherents of the earl of Kent who had supported and aided him in his plot to free the former Edward II a few months previously ("in bringing about the deliverance of our lord the king who is dead, whom God absolve") were also pardoned. On 7 December 1330, Kent's widow Margaret Wake and their young son Edmund, aged three or four, presented petitions asking for the record of treason against Kent to be expunged, partly on the grounds that "Sir Roger de Mortimer, late earl of March acknowledged at his death before the people that the said earl was wrongfully killed...". I'm going to cite a large part of the response to their petition because it states so often that Edward II was dead, really truly dead, and it was thus really, truly, completely, totally, entirely impossible for anyone to have freed him, to the point where the repetition becomes very amusing:
Mortimer, Bereford, Bayouse, Maltravers, Deveril "and other evil men of their faction plotting the death of the said earl of Kent in a deceitful manner by an agreement made between them, gave and caused the same earl to understand that the Lord Edward, late king of England, the father of our present lord the king, and brother of the said earl, was alive, when he had been dead for a long time. And they did this to encourage him to purchase the release of his said brother, as if it had been possible to do this, so that, by such a thing, they would have promoted the downfall of the said earl of Kent. And when they discovered that he, being thus deceived and misled by their false plotting, believed their words, and appearing to them to be willing to purchase the easement and the release of his same brother, which release was impossible to secure all that time seeing as he was already dead, as is said above, they then allowed most secret negotiations thereupon between them until they again saw they were able to entrap the same earl of Kent, and then they put to him that he had knowingly wished the said release to the prejudice of the king our present lord, which was completely impossible as is said above, finally reported it to the king and to others of his council in the parliament last summoned at Winchester...".