I don't think that romaji should ever be used at all. Using romaji would give you the idea that some sounds correspond directly with roman script languages' sounds, which most of you know is not true (especially with the r~ group). It's best to just start with hiragana without any romaji and just learn it by hearing
I grew up with Chinese (second language ouo), but at my little independent school thing, we were forced to learn French from 7th grade. Starting like 9th grade, I got really interested in learning even more languages