To begin with, no contemporary list was made, so all later lists must be suspect.  Even such an imposing document as the "Roll of Battle Abbey" is known only from copies made hundreds of years later — copies which do not agree with one another — of a supposed original that may, in fact, never have existed.  Having an ancestor's name listed on copies of the Roll no doubt had more to do with making a donation to the Abbey than the ancestor having accompanied William.  In any case, its lack of contemporaneity — by hundreds of years — makes the Roll of Battle Abbey mythology, not history.

The following is an excerpt from Cokayne's The Complete Peerage, rev. ed., vol. XII, postscript to Appendix L, pp. 47-48:  "Companions of the Conqueror" (regarding the 1066 Battle of Hastings).  These are the proven companions of William.

(#1-12 recorded by William of Poitiers, #13 portrayed in the battle scene on the Bayeux Tapestry, #14-15 named by Orderic.)

Five more who were certainly in the Duke's army and almost certainly at the battle:

 16. Geoffrey de Mowbray, Bishop of Coutances.
 17. Robert, Count of Mortain, afterwards first Earl of Cornwall.
 18. Wadard, believed to be a follower of the Bishop of Bayeux.
 19. Vital, believed to be a follower of the Bishop of Bayeux.
 20. Goubert d'Auffay, seigneur of Auffay.

(#16 named by William of Poitiers, #17-19 portrayed in the Bayeux Tapestry, #20 said by Orderic to have taken part in the English War before William became King of England.)