Any boa is a constrictor snake, fatal hugs from those guys. Dangerous reptiles can be friendly to humans they know very well, but any humans who want to keep them need a lot of training and, in most places, a certification or license. This is for the safety of both the animal and the keeper. I wouldn't recommend trying to keep one as a pet, especially if you don't have much experience with them.
EDIT: This information is incorrect. While it is important to be cautious and educated when adopting any pet (especially snakes which have a lot of misconceptions surrounding them and require so much preparation for a first-time keeper), a rosy boa is the cousin of the larger boa constrictor which usually only gets to be around 3-3.5 ft., sometimes 4, and boys are smaller. They do not require a license or certification and can be carried across state lines. Rosy boas are known for their temperament, which is very calm and slow, and curious, so you have to be careful still that they do not escape, as with any snake. But they are generally regarded as a friendly snake. They are small, yet calm like their bigger cousins. And because they are constrictors, they can "hug", which adds to our conception of them as a "nice snake", even though obviously you wouldn't let any snake throw a coil around your neck, that's just common sense.
Also, a snake "knowing someone well" does not make sense. Snakes get used to your scent but they don't seem to form psychological attachments to humans like a dog. Snakes are inherently wild. But as far as wild animals go, a rosy boa is a nice companion to keep.