That's actually harder to answer than you'd think. Is it sandy soil where water flows right through quickly, leaving it dry? It is clay soil where it just sits there until it evaporates? Is it a loamy soil where it takes a little while to drain through so the plant has time to absorb some, then the soil remains damp?

It is windy or fairly sheltered? Frequent winds evaporate more water from the plant and soil, faster, than fewer winds. Is there a lot of hardscape around them, increasing reflected, radiated heat, making them need more water? Or, is the bed they're in surrounded with lawns which reduce the water needs? There are actually several more variables which can affect how much water, how frequently, the plants may need. Can you give more particulars about where they are planted; any walls or sidewalks they may be up against; where you live so we have an idea of your heat/wind/aridity, etc.; soil type; exposure, etc.?

Without more information, any suggestions you'll get are shots in the dark and may not be appropriate. Kim

If you want to add mulch on top, it will keep the roots and soil cool and you will have to water fewer times than if you don't have mulch. Mulch makes all the difference in my yard. You need at least 3 or 4 inches over the root area but not piled up against the base of the rose canes. I like to let my plants drink in the morning and not at night so the leaves have a chance to dry off during the day.

The soil type is going to make a big big difference.
Sandy soil -- water needed again soon.

Clay soil -- water retained for a time.

It's way variable.

Jeri

Yes, "It's way variable," but plants use the same amount of water in a given climate regardless of soil type. Deep, heavy soils have the ability to retain water and also to lift water up from the subsoil through capillary action. But when the soil moisture runs short, a similar amount needs to be added each week to keep roses growing rapidly. For example, in a fairly hot month, you might apply five gallons once a week to clay soil vs. two gallons three times a week to sandy soil or shallow soil.

I am in So. Ca in Zone 9. I have 48 rose bushes that are well established (8-10 yr old). I had setup two 4GPH flag drippers per rose bush. Roses are in a raised Masonry planter that has mix of clay and sand. Planter sits on top of the slope so I am sure water runs down quickly.

Currently due to cooler weather I am watering them once a day for 2 minutes daily. that gets tham about 2 gals/week. Soil around and below is moist so I guess they are happy. I am seeing massive growth flush right now.

Pretty soon I am going to double my time to 4 minutes daily and that will get them about 4 gals/week. Because of where my planter is located, I have to water daily, and not water deep long times as water will run off. I am better off watering twice a day then watering once and let the water percolate down and not benefit the roses. Like someone said, Roses will drink only so much and what it doesnt drink goes deep in the ground. Why waste water.

5 gallons per week per plant is a good starting point. More for very sandy soil, super-hot dry weather, full blazing all-day sun; less for winter, cool weather, heavy clay, afternoon shade, and so on.

A thick organic mulch of shredded plant materials, compost, etc. will help to hold in moisture and keep the roots from getting too hot. Roses prefer that their roots not get too hot. In addition, as the mulch breaks down, it enriches the soil.