No. All items on Roblox’ catalog is protected by copyright law unless the creator specifically stated otherwise. If you still want to use an item in the catalog, contact the creator and say that you want to use an item(s) for a purpose. In the Roblox Library under the create tab, if “Allow Copying” is set to true, then it could be considered in the public domain, so copyright law doesn’t apply.
As for fair use, it doesn’t apply to this situation. The only time it applies is if you are commentating /critiquing the original work or you are doing a parody of the work.