Rosario asked Elizabeth Neumeier, Phillip LaPorte and James Oldham for a raise to $3.3 million, and Colorado argued during Tuesday's session that he should be paid $2.8 million.
A decision is expected Wednesday.
Rosario, who turns 26 on Feb. 23, hit .267 with 13 homers and 54 RBIs last year, down from .292 with 21 homers and 79 RBIs in 2013. He made $502,000 last year.
Teams lead players 5-3, and six cases remain scheduled for this week. These are the most hearings since teams were 8-6 in 2001.