Katakana: グラノラ
Hepburn: Guranora
Shuiesha: Granolah (?)
Viz: Granolah
The katakana is グラノラ (Guranora). Viz romanized it as "Granolah". It's not clear what Shuiesha romanizes it as, because I don't think we've ever seen the name officially romanized in Japan. The official Dragon Ball website's English translation went with "Granolah", but that website is machine-translated and full of errors. We don't know who came up with the "Granolah" spelling between Viz and Shuiesha.
The name is based on the food "granola", which is normally approximated to katakana as グラノーラ (guranōra), but it's sometimes also approximated as グラノラ (guranora) without any elongated syllables. Many food products use グラノラ (guranora). The only difference between the two katakana spellings is that one elongates the ノ (no) and the other doesn't. Not elongating the ノ (no) wouldn't result in a different word; it would just translate to "granola", only with the "no" said quicker.
The "Granolah" spelling doesn't work, because adding an "h" at the end only serves to elongate the last syllable; we can tell by the katakana that the ラ (ra) isn't elongated. I wouldn't go with "Granolla" (two "Ls") like Kanzenshuu does, either, because that just looks like a typo of "granola". If I was forced to spell it differently from the food, I might go with "Granora", "Guranora", or "Guranola", but there's no reason not to just use "Granola". Especially considering Japanese food products use グラノラ (guranora) for granola, anyway.
tl;dr His name is "Granola".
