I recently came across an article by Piotr Garbacz with the title "Runic Inscription on the Spearhead of Rozwadów (KJ 35): ik eruls or ik erlas?" (you can read it here; he has apparently two publications, which deal with this topic: –]krlus Jak rozumieć napis na grocie rozwadowskiej włóczni?, in: Anna Garbacz (red.), Z przeszłości miasta Rozwadowa. Muzeum Regionalne w Stalowej Woli 2015, 73-79 and Inskrypcja na grocie rozwadowskiej włóczni (KJ35): ik eruls czy ik erlas?, LingVaria 21 , 13-20).
He states that both 'readings' - ik eruls and ik erlas - are possible, although ik erlas seems a bit more likely. When, however, ik eruls is read, "[t]his reading would then be the only Germanic attestation of the continuant of Proto-Germanic *erulaz, found to date only in Greek and Latin sources (Lat. Eruli with variants ...)". He ascribes the form PGmc. *erulaz to a suffix variant next to PGmc. *erlaz and PGmc. *erilaz.
This, however, is incorrect. As was shown by Norbert Wagner (Zur Etymologie von Hermun-duri, BNF 43 , 407-410), the -u- in the name of the Eruli is due to an inner-Latin insertion (Vokaleinschub) between -r- and -l-; the Lat.-Gmc. name of the Eruli thus also reflects PGmc. *erlaz. The only suffix variants are therefore PGmc. *erlaz (continued e.g. in Lat.-Gmc. Eruli, OIcl. jarl) and PGmc. *erilaz (continued in Run. erilaz/irilaz). Now, a Germanic speaker would not insert this Latin -u-, so eruls is not to be expected.
More likely would indeed be (e/i)k erlas < PGmc. *erlaz, which would be interesting, because it would show a form with preserved -a-. For the dating of the syncope this is unfortunately not really helpful because the object has to be dated somewhere between 1-375/400 AD (cf. Lisbeth Imer, Jernalderens Runeindskrifter i Norden - Katalog 2015, 218). However, this (as any) reading and interpretation is far from secured (cf. e.g. Robert Nedoma, Schrift und Sprache in den ostgermanischen Runeninschriften, NOWELE 58/59 , 21f.); it remains even unclear, if the inscription contains runic characters at all (so on this blog). So it seems the best not to deduce anything on the basis of this inscription.