"Scrog" = "screen of green". Netting is fixed horizontally over the garden and any leafy growth that grows through the netting is gently bent back down under the netting. The result is a thick dense "screen" of "green". This is a good technique when growing under lamps, avoiding the need to move the lights further from the plants. For flowering plants a "scrog" system will yield one thick layer of flower buds, that is allowed to mature up through the netting.
Roll = 1.3m wide