Catalyzes the addition of further 2-8 glycerol phosphate units from CDP-glycerol to the single glycerol phosphate unit bound to the prenolpyrophosphate-linked disaccharide. The function in the cell is unknown since the product is not part of the poly(ribitol phosphate) teichoic acid found in the cell walls. 4-O-[(2R)-glycerylphospho]-N-acetyl-beta-D-mannosaminyl-(1->4)-N-acetyl-alpha-D-glucosaminyl di-trans,octa-cis-undecaprenyl diphosphate + n CDP-glycerol = 4-O-{[(2R)-1-glycerylphospho](n)-(2R)-1-glycerylphospho}-N-acetyl-beta-D-mannosaminyl-(1->4)-N-acetyl-alpha-D-glucosaminyl undecaprenyl diphosphate + n CMP + n H(+) The gene is not expressed under normal growth conditions. No effect. Belongs to the CDP-glycerol glycerophosphotransferase family.