I am unsure if it is just me, but managing a team on Roblox seems to have a lot of lackluster bits of information.
I am curious on an easy way to setup development, if there is a way, where a freelancer could access decals and nothing more to make UI. If I were to set up a non-group game, then all decal assets would have to be uploaded again, then the images on the UI would require a change when pushed into the actual game place to match the correct decals.
Is there a way to enable access to group decals without enabling access to other group games in the process? Enabling teamcreate on a group-game only allows permissions based on Role, but I assume there is no way to set a role up for a specific place or assets. Unless I am missing something, unsure where any resources on this matter are.
More detail would be good. However, you cannot set certain positions in studio. Roblox lacks in positions and access to certain roles. There is nothing I can do. You should suggest an idea in #platform-feedback.
Perhaps you should utilise external software to distribute information and assets to individual team members.
For my team, we use ClickUp for task management and we use Trello for asset management and storage (I know trello seems a strange thing to use for storage, but it links really well with other organisation and management systems we use).
This means that all team members have access to our assets and such, not just decals, without jeopardising the entire project through Roblox’s permissions. We can protect the overall game from immature developers who want to leak or destroy other people’s work - and we can efficiently create games!
For us it’s a win, win. You should try it!
Hope this helps,
-Tom 
This framework is basically already implemented on my side. What I am mainly trying to avoid is the uploading of image assets to a separate place which when brought into the actual game, all IDs within the UI will need to be changed to match the group assets. Unless I am missing something?