Just kill the sorcerer and the cleric, but more the sorcerer than the cleric, you just cannot keep a sorcerer away from his magic for long, moreover there is a chance he hasn't expended all slots by the time of capture and decides instead to play the fool while biding his time, all he needs is a single second level slot for rope trick in order to escape long enough fo the cleric to pray and replndish spells.
In games where Rope Trick is universal and unbeatable (don't get me started...), I doubt known spellcasters would ever be imprisoned in close proximity to appropriate lengths of rope.