My daughter is 4 months 2 weeks old and still not rolling over. Is this okay?

Yes. The average age for infants to begin rolling from their tummies to their backs is 4 months. Some babies roll earlier and some roll later. Some even skip rolling and just start to sit. Be sure to give your baby lots of "tummy time, ' when she can practice her rolling skills.
Putting infants to. sleep on their backs in their own cribs from birth significantly reduces the risk of SIDS. Infants who sleep supine roll front to back, sit in a tripod, creep, crawl & pull to a stand about a month later than the "old" average age, but attain those milestones within the normal age range. They walk & achieve all toddler motor skills at the average age, Back to Sleep" remains vitally important.