Round is an adjective and Around is an adverb.
Round describes a noun. It means circular........the round ball, the dish is round. It can also mean a completed set of events in a game or sport......a round of golf, a round of poker.

Around is used to describe a circular motion or movement........I walked around the chair, we traveled around the Earth.

To say "to revolve round the Earth" would be poor English, although many local dialects would use this form.