At the time he just chalked it up to eccentricity, but the episode came back to his mind when he returned home one day to find his street packed with federal agents.
He was shocked when the Drug Enforcement Agency informed him that the house across the street on the 3300 block of Ravenwood Drive was used to manufacture methamphetamine.
There was neither a telltale chemical smell nor the groups of strangers coming and going that signal a drug house, said Rosas, who formerly cleaned up meth labs in Florida.
"We never knew," said Rosas.
Often, neither do the families who move in after the bust.
A Pennsylvania couple recently made news when they got sick after purchasing their dream home. Tests showed trace amounts of methamphetamine left by the previous owners were giving them difficulty breathing, inflamed lungs, sore throats and headaches.
The family that moved in after the meth bust on Ravenwood Drive hasn't experienced any ill effects. But Kowanda Jimperson said she had no clue about the home's history when she bought it in July.
Meth is a powerful narcotic cooked using a host of toxic ingredients including battery acid, paint thinner and benzene. Cleaning up a lab requires thousands of dollars and hours of scrubbing, hosing and burning.
Georgia has no official standard, though, as to what's considered safe.
"No standards whatsoever," said Gordy Powell, the owner of Georgia Clean, a Smyrna-based industrial cleaning company that dismantles meth labs, among other things.
Powell follows Colorado's standards, which are the most strict in the country. He's trying out a new method to clean a meth house, which involves circulating super-heated air through the building for 12 to 15 hours. It's an improvement over at least two weeks of scrubbing the floors and walls of toxic fumes, Powell said.
"We're trying to extract what's been (soaked) into the walls," said Powell, who charges $10 per square foot for a cleaning.
If a house isn't properly cleaned, residents can be exposed to toxic chemicals through touching or breathing contaminated dust particles, according to the Georgia Department of Community Health.
State health officials are studying what health hazards are posed by methamphetamine residue, especially to infants and small children who are the most exposed to carpets and other porous materials.
At high enough levels, exposure may cause health effects similar to those experienced by meth users, according to the community health department.
Realtors aren't required to tell potential buyers that a home is a former meth lab, said Keith Hatcher, the senior director of public policy for the Georgia Association of Realtors.
Hatcher said known defects such as a leaky roof or a cracked foundation must be disclosed, but that doesn't apply to a home's history. It's the same for supposedly haunted houses or one where someone was killed, he said.
"That's not the way the law operates," said Hatcher. "It protects you against known danger."
Hatcher said while a Realtor doesn't have to disclose the history, a potential buyer has every right to ask about a house's former uses.
Another resource available to homeowners is the DEA's National Clandestine Laboratory Register, which discloses all known meth labs in a state going back to 2004.
The list shows Richmond County has the second-most labs in the state with 34, behind Walker County. Aiken County has 20 and Columbia County five.
The new owner of a home on Ravenwood Drive didn't know it had been used to make methamphetamine.