hmm
Rotovž was good but they've been closed for a while
otherwise I don't think I ate local traditional in Maribor itself (I'm there about two or three times a year, for business mostly)
now I can recommend you what to eat though – fried chicken is considered the traditional dish, and quick googling tells me you should go to "Gostilna pri lipi – Tašner" for that
btw check out the swans at riverside (take care not to step in their shit tho)