The 26-year-old centre-back has only been at the Stadio Olimpico for a year, notching up one goal in 30 Serie A games.
“He is a great defender and we are evaluating his situation,” Flamengo director general Paulo Pelaipe told Globoesporte.
“At the moment there are no actual negotiations for his signing, though.”
Castan arrived from Corinthians in July 2012 for €5m.
- Stadio Olimpico