The singer, who passed away unexpectedly on April 21, requested food that was easy to digest and "wasn't himself probably the last month or two," according to Roberts, who began cooking for Prince in 2013.
"I think he was just struggling with being sick a lot," Roberts told the AP, adding that Prince's hunger levels recently changed and that he appeared noticeably thinner.
Roberts cooked in the Paisley Park kitchen with his wife every day except Sunday, and sometimes even traveled on tour with Prince. He said he was usually tasked with crafting light salads and soup, and, more recently, smoothies.
Prince, who was a Jehovah's Witness, didn't eat meat, and, in fact, wouldn't allow it in his home. "If somebody wanted to eat meat, they would have to eat it in the parking lot. And he was very serious about this," Roberts revealed.
The "Purple Rain" singer's death is being investigated by the Drug Enforcement Administration, NBC reported earlier this week. Prescription painkillers were in the singer's possession when he died, according to the report. While the federal law enforcement officials wouldn't reveal what part the medications played in the star's death, they noted that the DEA will help determine the prescription's origins. A source previously confirmed to PEOPLE that Prince had a history of using percocet.
The singer's cause of death has yet to be revealed and the full toxicology report may take weeks to be completed.
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Roberts last saw Prince the evening before his death, and said he "wish[es] he was still here."
He said, "[Prince was a] caring, thoughtful person."