I cant agree about a fixed room — the style of drug taking means that users very often will inject or smoke their substance of choice within a relatively short time after ‘scoring’.
A drug purchase in Rhosddu is unlikely then to be consumed in another part of town where a room is available. There is evidence that the average time between purchase and consumptions less than 15 minutes- how many rooms would you need to set up to cover the town. Setting up one is the opening of the door for lots to be established — but in whose backyard?