Roblox UGC or User Generated Content is held in quite a high regard, and game developers often issue these UGCs to gamers for free by putting in little or negligible effort.

Much like most things on Roblox, you will be making this yourself from scratch, so you'll need to design a t-shirt in an image and then upload it to Roblox.

Roblox is rolling out Creator Hub, a new destination that gives developers more tools and centralizes things like documentation and a developer forum into one place.