Yes to pots, not really to general compost. They much prefer acidic growing conditions, so invest in a bag or two of ericaceous compost.
The shape of the pot might have some bearing on the plant - rhodedendrons and azaleas have relatively shallow roots so don't need deep pots - go for short and fat rather than tall and thin.

Also if you keep them in pots for years - which you can with slower growing ones - don't use pots whose tops curve in at the top - it is hellish trying to get mature plants out when you need to repot or change compost! Those ali baba types are best for annuals.