On the green plastic card that you receive when receiving your Rolex GMT-Master watch, you will find the name of the Rolex Dealer where the watch was purchased.
Regardless of whether you purchased the Rolex in their store or not, Rolex retailers provide aftercare service.
Rather than service your Rolex GMT-Master, the local Rolex retailer acts as a pickup and drop-off point. The authorized Rolex dealer can send back your Rolex watch for servicing if you drop it off. Rolex has a store locator on their website if you do not know where your nearest Rolex Boutique or Authorized Rolex store is.
Whether Google maps distinguishes between an official Rolex store and any other store that sells Rolex watches is unclear. Rolex.com, therefore, is the best resource for finding local Rolex dealers.