I don't think there was much scope to change the squad drastically for this tournament. Roy has only just finished with West Brom and so while he may be familiar with the players, he has virtually no time to assess different options. Also, he will be mindful of disrupting, on short-notice, a squad that qualified for the tournament fairly comfortably as it may negatively affect the dressing room.
GK choices were pretty straight forward.
Defenders:
-Richards omission was not entirely surprising IMO. With Glen Johnson assured of a staring berth just now, at least one back-up full backs had to be versatile. Having gone for Baines at LB, the RB would have to be the utility man. Smalling could have covered CB and RB, while Jones has covered both while offering an outlet in midfield. I'm sure Richards will be in contention for starting berth next season. Other than that, only Jagielka may feel a bit hard done by, but he's on the stand by list.
Midfield:
Apart from Downing and Henderson on the reserve list, there's not much I would change for the midfield. I would have taken either Johnson or the Ox, but not both seeing as Walcott and Young are in the squad. Long-term I would like to ditch Milner, but there's not too many choices for England at the moment.
Forwards:
Walcott's inclusion as a midfielder gives England the option of a 5th striker to cover for Rooney's suspension. Defoe is a goal scorer while Welbeck is definitely one for the future. I would have liked to see Holt, but with only one season in the top flight and no international exposure, I can see why Roy has gone for Carroll. I would have preferred him on the standby list ahead of Sturridge though. Sturridge has potential, but poor decision making and with Young, Walcott and O-C in the squad, we have similar players to call upon. Holt would have offered something different, particularly as an alternative to Carroll and I can see him being a handful for any defender. Crouch maybe a tad unlucky as well.
After this tournament, I'm sure there will be plenty of changes, but for now, it's probably the best England can do. I reckon we'll get past the group stages, but get knocked out in the QFs. If we're lucky, we might make the SFs.