Is a person who snores when sleeping necessarily getting rem sleep?

Most likely: In fact, snoring will usually increase during rem sleep. That is when the body is in its most relaxed state and prone to collapse of the structures in the upper airway. This will cause increased airway resistance and more snoring.

Yes: You can not predict if someone is getting rem sleep or not based on either the presence of absence of snoring. Snoring can be a sign of possible obstructive sleep apnea.

REM: Snoring alone does not necessarily preclude reaching rem sleep, although snoring usually does indicate constriction of the airway. When breathing is interrupted this is what usually interferes with the ability to reach deep restful sleep. The best way to determine the sleep patterns would be to have a sleep study done to determine if rem is being reached and how often breathing ceases each hour.