I would hope he will be a rotation player. Suns lost a lot of shooting with GA and RO leaving. Koa can't shoot to save his life, Bridges and Dunn are not great shooters either, and Kannard can't guard a chair. Highsmith is an outstanding defender, and a very good shooter, with high basketball IQ on top of that. They have to find him minutes. In my mind, Fleming is a backup 4, and Highsmith is a backup 3 who can get some run at the 2 as well. Koa is NOT going to be a rotation player this year. I love Dunn but right now, Highsmith is a more complete player. They need shooting, and Dunn is just a little behind. They need defense, and Kannard can't guard anyone.
Suns can run some interesting lineups with (for example) Goodwin, Highsmith, Dunn, Fleming, and Maluach, where everyone is outstanding defensively, and almost everyone is a competent three-point shooter. In my mind, Collin, Goodie, Highsmith, Fleming, and Maluach are the next five in rotation. Also, there will be some injuries, so everyone is gonna get some time to show what they can do.