Roses don't like a cedar mulch as the cedar gives off an oil which harm the roses. 6 inches thick will do if you are in a hot summer zone as roses like to have cool, damp roots.

The answer is a qualified No.
[From Hardy Roses: An Organic Guide to Growing Frost- and Disease-Resistant Varieties, by Robert Osborne, p. 27:] Inorganic mulches such as solid plastic sheeting exclude oxygen from the soil and should not be used... Modern landscape fabrics... are a nightmare if you want to work your soil... they are created from nonrenewable oil products... [Note: Osborne recommends aged manure and compost.]

I have also had problems with mulch encouraging powdery mildew. Also it encourages other fungus.