The phrase "roar off" generally refers to the sudden start or departure of something. There are several synonyms for the word "roar off" that can be used in different contexts. "Zoom away" is a great alternative when describing the fast departure of a car or bike. "Blast off" is another synonym that can be used when describing the take-off of an aircraft. "Race away" is another great option when referring to something moving at a quick speed, while "hurtle away" can be used when describing something that is moving rapidly and out of control. Other possible synonyms include "shoot off", "sprint away" and "jump off".