The pair have both been out injured recently, with captain Rolfes absent ever since suffering an ankle ligament problem during his side's 4-2 win over Hertha Berlin in August.
Rolfes required surgery, while Castro - another long-serving midfielder at the club - has been ruled out for over a month with a thigh problem.
While Leverkusen have coped well without the pair and sit fifth in the Bundesliga while topping Group C in the UEFA Champions League, coach Roger Schmidt will no doubt be pleased to see the experienced pair nearing a return.
"Gonzo may be in full team training in the next week," Bild quotes him as saying.
"And, like Simon, he will soon be available again."
Between them, Castro and Rolfes have made more than 500 appearances for Leverkusen during their time at the BayArena.
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