At the moment, it sadly seems like its not possible yet.
However the creator hub roles system is still in development and that they need to reimplement few features that legacy roles have but creator hub roles dont. (Especially the Rank system thing, which from what I know, is one of things to make that system using legacy roles.)
Hell, even the creator hub roles at the moment dont even let you configure the group outside the creator hub, even if you grant all permissions to that role.
I heavily recommend checking this forum post often to see if there are any new updates relating to the new roles.
Although, I do know another way you could do to have a “somewhat” rank system for your advanced Admin System for free. But the drawback is that it doesnt even use the GroupService and it requires you to manually update the list of ranks that people are in.
(Ppreferably in a script thats basically a list)
The second option is to basically merge the roles you want into a legacy role. So for example say you want to have two roles, one for admin and one for your alt accounts. You could just merge it into one (as long as the permissions are the same for those two roles.)
Theyre not great but its sadly the best you could do without spending robux on Legacy Roles. 
Oh and Ill just say this, but Im not a scripter myself. But the ideas I said about those two is possible to make.