"Many of the transition metals (orange) can have more than one charge. The notable exceptions are zinc (always +2), silver (always +1) and cadmium (always +2)." If some have set/constant ionic charges do they need roman numerals?

and my follow up question,
is it always necessary to use the Roman numeral as the assigned charge of the transition metal?(if so, why? why? do roman numeral need to be added to silver etc. if they already have set charges?)