A triangle doesn't have pitch, yaw and roll. If it did, what would it be your point of reference? It presumably wouldn't be the entity they belong to because all the triangles can point in different directions. So I guess it could be relative to a fixed axis, but it could still be +x, -x, +y, -y, +z or -z.
If you want to know which direction the triangle is facing, collisions give the normal, I think, or you could retrieve the triangle normal manually. If that's not what you want, then I'm not quite clear on what you're after.
If you want to know which direction the triangle is facing, collisions give the normal, I think, or you could retrieve the triangle normal manually. If that's not what you want, then I'm not quite clear on what you're after.