As you look at the depth chart there is still a need for speed and someone to stretch the defense. Tutu fills that need and has proven himself to the point where we know he can get open on deep routes and he can catch the ball. That said Jefferson and Skow both looked good last year. Jefferson and Kupp have both shown the ability to get open deep and both have decent speed so the long ball with be in play with or without Tutu.
Still I think Tutu gets some regular snaps as he will need to be accounted for when he is in the lineup with Stafford at QB.
Based on the depth chart I think Jefferson will take the snaps that went to Skow last year. Of course all this could change if the Rams decide to move on from Robinson & don't pick up another veteran. In that case Jefferson would move to WR2 with Skow being WR3 and Tutu coming in to open up the field vertically.
Not sure what is going on with Powell or if he will be resigned but Tutu may end up the PR/KR as well.
Getting everyone back healthy will be a great start and WR should is a position of strength IMO.