If Mark needs grass seed to Cover an area that is 16' wide by 16' deep Heavy looking to buy grass seed on a roll. The census daughter Grace to the store to buy this roll of seed and fertilizer combo. The role is 50' long by 4' wide how many rolls would Grace need to buy.. Please note that this is a roll of fertizer and seed. I do not need to know how many ounces of seed or how many pounds of seed that I need.