Catalyzes the addition of a second glycerol phosphate unit from CDP-glycerol to the prenolpyrophosphate-linked disaccharide, to complete the linkage unit. 4-O-[(2R)-glycerylphospho]-N-acetyl-beta-D-mannosaminyl-(1->4)-N-acetyl-alpha-D-glucosaminyl di-trans,octa-cis-undecaprenyl diphosphate + CDP-glycerol = 4-O-[di(2R)-glycerylphospho]-N-acetyl-beta-D-mannosaminyl-(1->4)-N-acetyl-alpha-D-glucosaminyl di-trans,octa-cis-undecaprenyl diphosphate + CMP + H(+) Cell wall biogenesis; poly(ribitol phosphate) teichoic acid biosynthesis. Belongs to the CDP-glycerol glycerophosphotransferase family.