Company Names, addresses, dates¹:
  Root Pop Bottling Co, 413 2nd Street, NW Washington DC (1944-1946)
  Root Rock Bottling Works, 413 2nd Street, NW Washington DC (1944-1946)
  Root Rock Ginger Ale Co, 413 2nd Street, NW Washington DC (1944-1949)

Notes:
I can't find Root Rock or Root Pop in city directories prior to 1944, but the obituary of Louis G. Harris (Washington Post, March 10, 1942) says that he came into the employ of the Root Rock Beverage Co in Washington DC in 1928. He was the General Manager of Root Rock when he died.


Root Rock Bottles:

(enlarge)	This is a 10" clear stippled crown top bottle with faded red & white markings: front: REFRESHING-HEALTHFUL / ROOT ROCK / FAMOUS FOR IT'S TASTE / Sparkling / Bracing / Beverage / ROOT ROCK / BEVERAGES back: Contains / FILTERED / CARBONATED WATER / CANE SUGAR / FLAVOR, CITRIC ACID / CERTIFIED COLOR / SEE CROWN / FOR OTHER INGREDIENTS. / CONTENTS ONE PINT / BOTTLED BY / ROOT ROCK BEVERAGES / WASHINGTON, D.C. bottom (embossing): ROOT ROCK BEVERAGES / WASHINGTON, D.C.
(enlarge)	This is similar to the above bottle, except that it is not stipled, and the markings are all white with no red. It is a 10" aqua crown top bottle with white markings: front: REFRESHING-HEALTHFUL / ROOT ROCK / FAMOUS FOR IT'S TASTE / Sparkling / Bracing / Beverage / ROOT ROCK / BEVERAGES back: Contains / FILTERED / CARBONATED WATER / CANE SUGAR / FLAVOR, CITRIC ACID / CERTIFIED COLOR / SEE CROWN / FOR OTHER INGREDIENTS. / CONTENTS ONE PINT / BOTTLED BY / ROOT ROCK BEVERAGES / WASHINGTON, D.C. bottom (embossing): ROOT ROCK BEVERAGES / WASHINGTON, D.C.
(enlarge)	This is similar to the above bottle, except the color of the glass is green. It is a 10" green crown top bottle with white markings: front: REFRESHING-HEALTHFUL / ROOT ROCK / FAMOUS FOR IT'S TASTE / Sparkling / Bracing / Beverage / ROOT ROCK / BEVERAGES back: Contains / FILTERED / CARBONATED WATER / CANE SUGAR / FLAVOR, CITRIC ACID / CERTIFIED COLOR / SEE CROWN / FOR OTHER INGREDIENTS. / CONTENTS ONE PINT / BOTTLED BY / ROOT ROCK BEVERAGES / WASHINGTON, D.C.
(enlarge)	This is a clear 9.2" crown top bottle. One of the circles seems like it has an upside-down heart etched in it - I'm not sure if this was by design or if it's a defect. Definitely doesn't look like a bubble-burst. Bottle is embossed: front: ROOT ROCK / BEVERAGES / CONTENTS 9 FL OZS back: ROOT ROCK / BEVERAGES / DESIGN PATENT 81642 bottom: 7314 2B40 WASHINGTON DC

(enlarge)	This is a clear 9.2" crown top bottle embossed: front: ROOT POP / BOTTLING CO / INC / CONTENTS 9 FL. OZS. back: ROOT POP / BOTTLING CO / INC / DESIGN PATENT 81642 bottom: WASHINGTON DC / (G in a square) / 149-1 This bottle has the same design pattern as one of the root-rock bottles above.
(enlarge)	This is a clear 9.5" crown top bottle embossed: front: Root Pop / BOTTLING CO, INC/ WASHINGTON, D.C. / CONTENTS 9 FL OZ. PAT APPLIED FOR