The Spain international is eagerly anticipating this week's Champions League clash, and has warned that the Blancos cannot afford to lose focus
Ramos feels that the Dutchman is in better form than ever before, while stressing that Rooney has the quality to cause Madrid problems as well.
"Van Persie is on very, very good form. We hadn't seen him this good for years. He's quick, strikes the ball well, he's a constant nuisance," Sergio Ramos was quoted as saying by The Guardian.
"Rooney's different. He's hard-work, heavy going. He enjoys the physical challenge. I prefer that, to be honest. I like that defender versus striker battle, that challenge.
"But Rooney's mobility is difficult: you don't always know how far to step out to pressure him. He drops deeper, or pulls wide and you wonder whether to follow.
"The communication with the midfield is vital. If he drops, there's a point at which the centre-back can't follow him and the responsibility passes to the midfielders. Go too far and you leave space behind."
Wednesday's first leg at the Santiago Bernabeu is scheduled to kick off at 19:45GMT.