I'd agree that some sort of Drip irrigation is what you are looking for. The main issue with tying into an existing sprikler system is that drip irrigation systems require that the water get filtered because the emitters use very small openings that can quickly get clogged. The good news is that if you use the retrofit Wet Boots is talking about, the filter is included in the retro-kit. If you do it some other way, you'll have to insure that you filter the thing your self.
Of course one issue you might find yourself fighting is the likelyhood that the pots require watering at a different schedule than the flower bed.
I have roses both in flower beds and in pots. Here in the deep south, I find that roses in pot need watering every day while those in the ground can go every other to every third day.