The likes of Giannelli Imbula and Bojan will return from loan spells, and Rowett has warned that although he remains "open-minded", he will also be ruthless if players aren't up to scratch.
Rowett said: "Every player that turns up for pre-season will have a relatively clean slate. It won't be a completely clean slate because as a manager in the Championship, with a knowledge of the Premier, having played there and watched and studied it, then there's going to be players you know will fit into your system – and some who will not.
"I don't think you've ever got a completely clean slate but it's a nice little analogy to us. A slightly smudged slate!
"Again I'm open-minded. I won't always judge previous performances on what I think I can get out of them next season. I'll look at the players I think can do more or be put in a position that helps them to flourish.
"But I won't waste time on players I don't think are quite my type in terms of their characteristics. I think that helps everybody because the more honest you are with people the more they appreciate it."