Coaches have mentioned that Casey is extremely intelligent and a sponge. Tight Ends love him, from what I've heard, and he's got a big enough name to help with recruiting. He's also involved with Special Teams.
I wouldn't say tight ends have a minimal role on offense. Just because they aren't catching balls doesn't mean they aren't heavily involved in blocking. Brooker played almost every snap against Arizona and the team ran a lot of plays that required Brooker to make a key block.