That's Texas. It is normal. Not many RVs are built to deal with really hot, humid climates and sun loads.
Come out onto the southern Great Plains in July or August and the roof air will run full time during the day, and might not keep the coach cool, until the sun goes down.
How well it works at night depends on what "cool" means to you. When it is 95-105F outside, "cool" for me means about 80F in the house, a little higher in the RV because the vents will be blowing air 15-20 F colder directly on me.
When I lived in Michigan I thought 80 was hot.