cover 3 roll

This sounds like rotation to me. We used to run this coverage in the 70's and 80's. The defense can rotate in one of two ways: first, the defense can predetermine the rotation. By this I mean that the secondary will know, before the snap, which way it will rotate. The second way has the secondary will rotate based on a key (meaning ball or a specific player-TB, FB, etc.).

The way you describe this coverage is correct except that the backside OLB is more of a backside curl player. If the defense is rotating one way, the chances of the ball being thrown deep the other way are slim.

When we ran this coverage, we would stunt an OLB and play this coverage behind it. We viewed it as a run coverage.