Where it is customary to eat roast [meat] on the nights of Pesach, we may eat [it]; where it is customary not to eat [roast], we may not eat [it].  Where it is customary to light [lamps] on the nights of Yom Kippur, we may light [them]; where it is customary not to light [them], we may not light [them]. But [in all places] we light [lamps] in synagogues, houses of study, dark alleys, and for the sick.