There was this one episode where everyone on the ship had amnesia, and the two of them were unable to remember all the run-ins they'd had and got along so well they jumped into bed together. I thought: "well they've finally figured out they ought to really like each other!" I reckon they should have made a regular pair - Ro suits Riker a lot more than Troi does. Turned out the flip-side of the reason they kept locking horns was how much alike they are. They share the same temperament - both adventurous, both headstrong, neither has much patience with incompetence. I'd have loved to see them go on some really dangerous missions together.
Ro and Riker would have only been "friends with benefits" at the most. Troi was always his main squeeze.
I think Riker and Ro could have been a good on again-off again fling if they had met in a context of equals where one did not have authority over the other.