To get back on topic... I think it was indirectly explained. The Romulans were given a hospital base on one of Bajor's moon's. Since DS9 is at the mouth of the wormhole, we don't see Romulan ships as often because they are likely stationed near their hospital base. Instead of shore leave on the station, they can go to the planet. If a ship needs to be docked for repairs, then that ship goes to the station. It wasn't clear if the base was removed or the weapons were removed after the their blockade.
I also would not be surprised if the Romulans were not around DS9 as much because they were fighting a different front. Since their systems were vulnerable to Breen weapons, and the Klingons were picking up a lot of slack for both the Federation and the Romulans, it would make sense that the Romulans would take defensive positions.
If the Romulans were stationed near a Federation starbase, I assume Starbase 375 would be the best option. It's near the front lines, and Admiral Ross has an amicable relationship with the Romulans. Their cloaking technology also allows them to hide near the boarder, and serve as backup should the need arise.