Answer: The Gemara (Berachos 42a) writes that one recites mezonos before eating pas haba b’kisnin. It isn’t clear, however, what this includes. The Shulchan Aruch (OC 168:7) writes that one recites mezonos on bread that is baked with honey, milk or fruit juice providing that one can taste the difference between normal bread. The Rema writes that one would only recite mezonos on such bread if it also contains a significant amount of juice or spices (see Taz 168:7; Darchei Moshe 20). The Mishna Berura (168:33) paskens that this liquid needs to be the primary ingredient and one would have to be able to taste the difference in the bread. Accordingly, one would have to wash and recite hamotzi on regular mezonos bread which tastes similar to regular bread (See The Laws of B’rachos p254).
Many quote the Da’as Torah (168:7) as allowing one to recite mezonos (and not having to wash and bentsch) even if one can’t taste the juice, providing that the main ingredient is juice, etc. R’ Yisroel Belsky points out that one can’t rely on this as he was referring to specific ingredients no longer used in baking.
Dayan Gavriel Krausz (Mekor Habracha 14) writes that there is a safek as to whether one needs to wash and recite hamotzi before eating bridge rolls or not, though writes that providing that they contain fruit juice, one can rely on the lenient view and recite mezonos.The Mishna Berura (168:24) writes that if one eats a meal’s worth of pas haba b’kisnin, one needs to treat it as regular bread. This is true even if one ate a little, together with other food. Thus, even one who made mezonos before eating a couple of bridge rolls (or a slice of pizza) followed by some salad, may have to bench if he is full. Many rabbonim therefore urge Baalei Simcha not to serve bridge rolls at their Simcha.