I want to know the correct romanization for ベオウルフ.
For me, it's Beōrufu, because the pronunciation of Be-o-wulf has a long vowel (oo/ou/ow/oh). However, some people discord for being a foreign name.
Firstly, using the macron for indicating long vowels is only really used in (Revised) Hepburn romanization, so "correct" would mean "according to the rules of Hepburn romanization".
Secondly, Hepburn only uses ō for long vowels and here there isn't one! One way that points to this fact is that the word in katakana isn't spelled オー, but オウ.
Actually, ベオウルフ is a good transcription because for one it reflects the fact that the ウ is a substitution for "wu" (definitely not a lengthener of "o"); further, it suggest the pitch as ベオウルフ【LHHLL】, whereas ベオールフ would have to be ベオールフ【LHLLL】 (the former is much closer to the English pronunciation, which has a secondary stress at "wu").
In any case, I think you should romanize ベオウルフ as beourufu in Hepburn and as beouruhu in Nihon-shiki/Kunrei-shiki/Wāpuro.