An offer has been made to purchase Rosecroft Raceway, according to track official Earle Palmer Brown, who has notified stockholders of the possible sale.

A letter signed by Brown, chairman of the board of directors of the Oxon Hill track, told stockholders the board would take 10 days to study the "fairness of the offer" and report back. The letter was dated Sept. 10.

Brown's letter called the offer "an unexpected and unsolicited expression of interest" in purchasing the track. The letter also said the proposal to purchase Rosecroft stock was "appreciably higher" than any other offer the track has received in the past.

Brown declined to name the potential buyer. He did say the offer was made by someone not currently in racing, but who was interested in continuing to operate Rosecroft as a race track.

William Miller, president and general manager of Rosecroft, confirmed the offer for the track but declined to name the interested potential buyer.

Frank De Francis, who holds ownership interests in Freestate, Pimlico and Laurel race tracks, said he was "categorically not" interested in Rosecroft and has not made an offer to buy it.

Rosecroft, which opened in 1949, is just off Exit 4 on the Beltway in Oxon Hill.

No one holds a majority interest in Rosecroft, according to the latest unaudited list of shareholders filed with the Maryland Racing Commission. As of June 30, 1986, the person with the largest number of shares was Vivian M. Densford with 176. Miller (165 shares) and Brown (153) are the next two largest shareholders.

According to the report, there are 2,948 shares of Rosecroft common stock, and another 802 shares are held in treasury. Brown declined to comment on Rosecroft's value or the specifics of the offer.

Last year, Rosecroft purchased a majority share in Ocean Downs near Ocean City, Md., for $1,989,270; it was renamed Delmarva Downs this year. It is not known how Delmarva Downs would be affected by a purchase of Rosecroft.