I for one have NEVER met anyone over 3 years old who could not pronounce a proper R, but I see such people on TV relatively often. So it's probably impossible to judge how often it happens based on personal experience only, and I believe there's no statistical data on it either.
Is it difficult for you to pronounce this letter? If so, how do you practice?
Try to search on Youtube for "rolling R". There are a lot of tutorials and various videos for Spanish learners (Spanish and Russian R's are identical).

This kid from Hong Kong learned to roll his R's in two months. Maybe you can ask his teacher for advice.