Sort priority in Navigational ROles and Worksets

Hi

We had No of Navigational Roles and No of worksets assigned to each roles.

We are performing role merge

How i acheieve the below

If a user is assigned with 4 different navigational roles...my requirment is sequence of display of worksets would

All worksets in Role1 and then all worksets in role3 and then role 2 and then role4

How can i get this

Thanks in advance