Ashley, this is totally unfair, because the roster I'm going to set out is not my ideal. My ideal roster would be built around Max Scherzer and Justin Verlander. But I think the question that you are really asking is who should be called up to make this September less miserable.
First all, congratulations Tigers -- you already promoted my 2 favorite choices -- W. Castro and J. Rogers. Good job. Took you long enough!
We are certain to see the returns of Greiner, Candelario and Stewart. 2 of the 3 should be here already, and would be if the Tigers didn't feel the need to hold on to mediocre players with a GI Joe Kung Fu grip.
I'm assuming that we will not see Matt Manning or Tarik Skubal, and I guess that's ok -- even though they would sell tickets. I wouldn't call them up either.
Daz Cameron won't be called up, but maybe he should be. He's likely to spend most of next year in the Minors, so the often-raised service time issues don't mean anything. Despite being very, very young for the International League, Daz actually leads the entire Tigers organization at any level in walks. In fact, it's not that close, with only Isaac Paredes and Jacob Robson within 10 walks of Daz. Daz hasn't had a good year, but he's been pushed and has sort of held his own, more or less.
Speaking of Robson, I have a novel idea for the Tigers -- although Harold Castro has been a pleasant surprise, it would be nice to play an outfielder in Center Field, wouldn't it. Against pitchers younger than him, Robson has hit .325/.396/.450 this year. The fact that he hasn't hit particularly well against the much-older mix of MLB veterans that populate Triple A in 2019 doesn't mean that he isn't still a moderate prospect. It is worth seeing what he has.
I'd call up Frank Schwindel. He's only 27, and he actually is a first baseman. Enough of the Mercer/Hicks platoon at first. The Great Rock 'n Roll Schwindel has hit .367/.398/.714 at Toledo with 9 homers in 103 plate appearances. Given that power, there is no excuse for a sub-5% walk rate, but there is no excuse for playing a Mercer/Hicks platoon for the rest of the year either.
Although Mikie Mahtook leads the Tigers organization with 21 homers in 2019, he's 29 years old, and I wouldn't bring him up.
I think that's it for position players.
As far as pitchers go, might as well call up Funkhouser. He's been terrible at Triple A, but he's 26 and has to be added to the 40-Man or lost. A 7.3/9 BB rate won't cut it, but they might as well work with him.
I'd call Schreiber back up. He deserves more than a 2 outing shot.
Tim Adleman has definitely been worthy of some year-end starts. He's 31, he won't be there for the future, but he's pitched well (a rare thing in the International League this year). He wouldn't embarrass the team, although they might embarrass themselves.
The Eduardo Jiminez roller coaster will continue its circuit. That's assuming he isn't currently on the roster. Who can tell? If Tyler Alexander is down, he comes up also.
Finally, Bryan Garcia deserves a tryout at this point. Assuming he's healthy.
Well, this has been a fairly depressing exercise. Even trying to be interesting, the most interesting players are Robson, Schwindel, Schreiber and Garcia. Oh, and Candelario and Stewart, but those are MLB transitional players being left in Toledo by a mediocre front office.