Roller, ngumunye wemithombo enkulu kakhulu yombhidi, kungaba khona amakhulu, kungathola ukukhokhela umkhombandlela wokukhomba nokwakhiwa kwemithombo. Iyinhloko yezimali ezingu-35% yombhidi yonke yombhidi futhi iyakwakha ngaphezulu kwezinye zezikhali, ngakho-ke ubuciko bokuthengiswa kwezikhali kuyisikhathi esisodwa. Iyakwakhiwa ngomkhiqizo kanye neplastiki.