1
general::
Phrase(s): get the ball rolling [and] set the ball rolling; start the ball rolling
Fig. to get a process started. (See also keep the ball rolling.) • If I could just get the ball rolling, then other people would help. • Who else would start the ball rolling? • I had the ball rolling, but no one helped me with the project.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Also, keep the ball rolling. Start an undertaking; also, keep an undertaking from flagging. For example, Let's get the ball rolling by putting up some posters, or The hostess kept the ball rolling, talking to each of the guests in turn. This expression originated in one or another sport in which it was important to keep a ball moving. [Colloquial; late 1700s] Also see GET THE SHOW ON THE ROAD.
American Heritage Idioms