Create Separate group of users for merge requests approvers and who can merge on protected branches

How to create Separate group of users for merge request approvals and one for who can merge on protected branches.

Right now we have two level of controls one at merge request approvals and one at who can actually merge on a protected branch.

But we wanted to create a separate group of users and allow access for the either of the above two case.

Is there a way possible to create a custom role based group of users or any other way to handle the above need.