Rosa is being held in Chester County Prison and faces charges including possession of child pornography, sexual assault and child rape.
According to authorities, detectives were alerted to cyber tips in March. While executing a search warrant at Rosa's home in West Whiteland Township, investigators said they discovered video recordings and images of sexual abuse in six Gmail accounts and on his cellphone.
"The adult women appear to be unconscious, and therefore they may not know that they have been victimized," Chester County District Attorney Christopher de Barrena-Sarobe said during a news conference on Monday afternoon
Investigators said many of the people depicted in the videos and images have not been identified.
"The unidentified children abused by the defendant appear to be under ten years of age," the district attorney said.
Authorities said Rosa worked as a handyman and painter and previously lived in Philadelphia, Malvern, Allentown and Saylorsburg. Detectives are seeking information from anyone who may have spent time with him or hired him for work.
Pa. handyman facing child rape charges
Investigators are concerned Rosa may have gained access to victims through work he performed in their homes. In at least one case, authorities said, he asked to stay with a family while completing work at the residence.
"We have some belief that he may not have known his victims very well. That he may have been doing work for people in their houses. Asked to stay in those houses for a day or two, and may have cultivated his victims that way," the district attorney said.
The juvenile victims are believed to be under ten years old.
Investigators are also attempting to identify the location of a room depicted in one of the images recovered during the investigation.
Rosa's attorney declined to comment on the charges. Authorities continue to seek information that could help identify additional victims and further the investigation.