American Invsco, a Chicago firm believed to be the largest condominium converter in the country, this week denied that it had bought the Grosvenor Park Apartment complex in Roxkville.

But court records in Maryland and Chicago disclosed yesterday that the complex's two high-rise towers and garden apartments were bought for $30.4 million by a partnership called Rockville-Grosvenor Associates, whose officers were executives at American Invsco.

A spokesman for the company said earlier this week that a partnership that wanted to remain secret, had bought the 629 high-rise apartment units and 421 garden apartments at Rockville Pike and Grosvenor Lane.

Court records in Chicago showed that the president of the partnership is Bruce Lord, a senior vice president at American Invsco. The partnership's secretary is listed as Mark S. Goldstein, of Invsco's legal and taxation department.

Neither Goldstein of Lord could be reached for comment yesterday and an Invsco spokesman said he was unaware of Rockville-Grosvenor Associates.

According to sources in Chicago, Invsco is doing a billion-dollar business in real estate transactions in Chicago and a few other cities and is attempting to branch out nationwide. Because of a bad reception in Chicago of its hard-sell expansionary policies, Invsco is now trying to shed its aggressive image and acquire property quietly, another source said.

Invsco is headed by Nicholas Gouletas, a 40-year-old native of Athens, Greece who built Invsco with his sister and brother.

According to Forbes magazine, Invsco spread into New York when it bought the 28-story 900 Park Avenue building for $20 million, but met resistance when it tried to expand into Grand Rapids, Mich.