When I first started playing ice, I couldn't stop sliding out of the crease. When I finally was able to control it, it caused problems in roller, as I would slide post to post, only to watch a puck roll between my pad and the pole, cause I didn't slide far enough (I would have hit the pole with the same exertion in ice). Also, in roller, everything was a t-glide, or a pad slide across the crease. I rarely do the t-slide in ice, as it is easier (and sometimes faster) to shuffle. and the pad slide back and forth is much easier on ice than on roller. That should be no surprise. The differences were not exactly night and day, but they were enough to convince me to choose one or the other, instead of playing both.
As for skating skills for goalies... I am on the goalie-should-be-a-great-skater bandwagon. You gotta be fast, both forwards and backwards, and side to side. You gotta be able to do it in control, and stop on a dime, incase you gotta change directions in the middle of a play. It is certainly possible to play goal with poor skating skills (Roller teams are often guilty of this), but in my experience, the better goalies are usually the better skaters as well.