i think you kinda overstate Roxys powers a little. The only thing we see her create on her own are generic cubes, only being able to make anything else by having a space player help her

Cubes, Pumpkins AND Wizards- That is, basic things, voidy things, and her interests. This is after less than a day training to do stuff, and when she faces Condy she’s already learned to use the PGO as building blocks to make more complex things like Fists and a Pony- Which also spawns with an actual ribbon! Post-canon she could really become sort of like an alchemiter herself. Specially since she’s dating Callie, always got that Creative Muse around to inspire her finger-twiddling.