Hello Snailman!
Roof trusses are manufactured and dimensioned according to the conditions you have.
If they are to be free-standing, the truss is adjusted accordingly.
However, you get quite large and cumbersome constructions if the span becomes too large.
However, it should not be a problem if the house stays within reasonable proportions.
If you buy prefabricated standard trusses, you should receive a specification on how these should be assembled.