He's come into the game trying to be unselfish, trying to move the ball, and trying to be a PG. The problem is that other then Jaylen Brown (surprisingly enough) there's nobody on that second unit who has been even remotely capable of actually putting the ball in the basket. Jerebko can only hit wide open threes, Zeller looks lost, and Marcus Smart makes Rajon Rondo look like Steph Curry.
So after 10-15 minutes of trying to be unselfish (and seeing that it's gonig nowhere at all), he's making the adjustment in the second half, taking over the game, and making things happen.
Scal even made a comment in the first half of the first game, criticizing Rozier for not being aggressive enough and for playing too passive - he's trying to find the balance and learn when to be unselfish, when to take over.
From what I've seen so far it seems that when he wants to take over, he can do so pretty much at will. So when he's taking 3 or 4 FGA in the entire first half it's not because he can't get the shots off, it's just because he's trying to be a team player and play unselfishly.
Moral of the story - if you want Rozier to play unselfishly, then put him on the court with some guys who can actually make shots. Smart's shooting is depressing beyond words.
It's also worth remembering that these are pre-season games, so essentially practice. We as fans don't know what the coaching staff has told any particular player to work on, or for the veterans, what they've decided to work on. So in Rozier's case, maybe the coaches told him to try and be a facilitator in the 1st half, and then told him to shoot more in the 2nd half. Or in the 1st game the other night, people were concerned that IT was passing more than shooting. It's likely that he was doing that deliberately, both to work on his passing game, but also to avoid hard contact at the basket in a meaningless game. He already knows he can make those shots, and so does everyone else. No reason to do it in practice. As we get closer to playing meaningful games, I'm sure we'll see a lot of these guys playing more like we expect them to in the regular season.
-V