I'm not quite sure what you mean by "required." Are you referring to forms that literally won't accept romaji, or forms that just say "Name in kanji" and "Name in kana" or similar, with the implication that that's what's required/wanted but actually will take anything? My suggesting is in all situations other than when the form won't accept roman characters as a technically-enforced rule, put in roman characters for your name even if the instructions on the form don't account for this. Whomever is reading the information will figure out that you're a foreigner and don't have a Kanji representation of your name. And, if some subsequent system requires a foreign name in katakana, they'll probably transliterate it for you.