You can expand your rosters to 40 men due to Sept. 1st call-ups. Keep in mind come October if you make the playoffs or if you don't, you will have to reduce your roster to 25 men again, especially if you call up way too many. You don't have to make call-ups, but feel free if you feel it will help your team or a certain player.
Other than that, 15 game sim Monday night. Same thing, try to get line-ups in an hour before hand because that's when I'm going to try to start the sim process and then uploading and everything (atleast that's what I did tonight).