With any plant if you water regularly they think, how happy I am with this water supply now I don't need to put roots down. If they are all root close to the surface they will suffer in dry weather. A mulch will help keep the moisture in. You could also put something in the ground, such as a pipe, so that when you water it goes further down and the roots will go after it. That's the theory anyway. Good luck.

Hello, Frenzy!
Here in the southern Arizona desert, we would water roses in such an area around 18 inches deep--2-4 inches of flood irrigation, or 5-7 gallons of drip per emitter--every 2-3 days in summer. Also, we would put a 2-3 inch deep mulch over the soil to keep the roots cool and moist. I don't know what area you garden in, but I understand that much of the US has been getting Arizona temps the last few weeks!