Hi – thanks for your email. You wrote asking if Roses are toxic to dogs. There are no toxic ingredients in roses that are life threatening however the fleas can cause oral and gastric irritation. Some dogs will drool and vomit.
I'd recommend that you rinse her mouth to help get any plant material and the "taste" out of her mouth. Also, make sure that she has no continued exposure to the plant.
Generally most dogs feel better after they vomit and get the plant out of their system. If the vomiting continues, please call your veterinarian for examination.
An article that might be helpful to you is Toxicity of Common Cut Flowers
Best of luck!