Comma List vs Multiple Records
Please, don't store comma-separated lists in a single column. This is just a disaster waiting to happen. If these are separate facts, they should be stored separately. 

Table GroupMemberRoles
GroupID  FK
UserID   FK
RoleID   FK
(PK on all three, with perhaps other constraints)


Your queries (say, to find the admins of a certain group) should be of the form: 

WHERE RoleID = 1 AND GroupID = @GroupID;


And NOT:

WHERE RoleID = 1 AND ',' + GroupIDList + ',' LIKE ',' + RTRIM(@GroupID) + ','; 


Or to find which groups a user is an admin of should be similarly simple:

WHERE RoleID = 1 AND UserID = @UserID;