I read that a way to bypass a magical trap is by doing a dispel on it. If it succeds, it is affected like an item :
If the object that you target is a magic item, you make a dispel check against the item’s caster level (DC = 11 + the item’s caster level). If you succeed, all the item’s magical properties are suppressed for 1d4 rounds, after which the item recovers its magical properties.
Who is supposed to make the 1d4 throw for the suppression effect duration ? The one doing the dispel ? or the GM ?