I gather you mean battens rather than trusses.Yes, you'll need to fit battens parrallel to the hips, spacing depends on what ridge capping you're using. From memory I think you go 200mm either side for roll top ridge, however if you have a steep roof pitch you may need to reduce this spacing as the angle changes how the ridge lines up to the batten. Too hard to explain in words, if in doubt get a couple of batten offcuts and a bit of ridge and mock it up to get the right spacing.
Mick