Ads per role

Hi! I have a site which is based on roles to identify the user's profile who is surfing it.

First I created different ads groups for each role and I put the blocks one below the other, but if one user has two or more roles, he views two or more ads one below the other.

Then I installed the Nodeaccess module. I thought if I created only one group for all the ads and I grant view permissions for each role in each ad, the 'ad block' would displays randomly the permited ads. This module works perfectly with all content types, but not with Advertisment Type.

I didn't explore the ad module deeply because is huge! So I don't know if this feature already exists, but it will be a great feature!

My idea:

In Ads Creation Form add some checkboxes with the roles (defined at ads settings in administration page). The selected roles must be able to see the ad. If none role is selected, all roles must be able to see the ad.

thanks for taking time to read me :)