Pop-up COVID booster clinic coming to Rossmoor on Nov. 1 A pop-up COVID-19 booster clinic will be held in Rossmoor on Tuesday, Nov. 1 from 9 a.m. to noon at Stanley Dollar Clubhouse. Advance registration is required to receive the booster at the clinic offered by Contra Costa Health Services (CCHS). Residents only need to provide their name, address, phone number and email when registering.