I'm easily amused.
Since you have flower pots, and that could mean many things, i would probably set the root zone to the average root depth. Some roses are like the terminator of plants so they can afford a touch of drought...I'll assume yours will as well.
not knowing the setup, I have a few 100 gallon pots with maples and various pots between 10-30 gallons all connected to a drip zone with trees and shrubs. I use 2gph emitters on most vegitation except my smaller pots, they get .5-1 gph emitters and my trees have 2-3 2gph. This is obviously a hetogenous mix and so root size can not be determined. So I set my root depth to 10 inches with an efficiency of 100% and I run the drip for 40 minutes on a flex schedule. So far so good, things make it through peak heat last season and I'm not wasting too much water by over watering the smaller pots. This occurs every 7-8 days right now and will increase to every 3 days during the summer. All,of this is on flex though. Even my pots with annuals, I use miracle grow water saving crystals and that carries those pots the 3 days in 90+ temps.
If I recall from another post you have the drip tub with built in emitters. You could achieve this same effect by installing just enough drip tube to contain a limited number of emitters and run the emitter less drip tub between pots and vegitation. Take a few wraps of tube with emitters where you need more water. But this can become a pain, which is why I switched over to the tubing without emitters.