From the article, really buried: "Roiland usually asked people how old they were, if they were single, and if they were “into girls.” In three cases, when the person said they were under 18, Roiland would message them again months or years later. Those three conversations started with people who said they were 16 at the time, and continued for years, until they were 18 and older."
After reading the whole article it doesn't seem like he did anything sexual with anyone under 18. My takeaway is that he's a creep, abuses his fame and power (part of a big club there), he's manipulative, and he plies underage people with alcohol to get them to sleep with him, but it appears he's not a pedo. Or at least smart enough not to get caught.