If you're talking about removing something from your inventory:
If you bought something on ROBLOX, it's final. ROBLOX has 3D view for a reason. Not only that, you can easily go into Studio to see what it looks like on your avatar.
What I think is that once you buy something, then it's yours. And you pay for it. When you decide to remove it from your inventory, then go ahead. Just don't expect a refund.