A Washington development firm has proposed a 19-story office building in Rosslyn that an Arlington planner said yesterday should complete the development of the high-rise area.

The plan from the Kaempfer Co. also would add two small parks in office-congested Rosslyn in return for the County Board's granting the firm extra density for a triangular-shaped office building at 1001 N. 19th St.

County planning chief Gary Kirkbride said that the plan, if approved, "should just about finish off Rosslyn," where virtually every parcel is developed or awaiting construction.

Only one other large piece of land is still vacant: a site at the corner of N. Kent Street and Wilson Boulevard, which the county has designated for hotel or residential construction and the developer wants to use for offices.

John Tyers, marketing director of the Kaempfer Co., said the firm hopes to transfer density rights from two other small pieces of Rosslyn property it owns to the office building site. He declined to give the project's cost, but said it was greater than one estimate of $25 million.

The office site and a wedge-shaped parcel just to the north between N. Lynn Street and I-66 are in a special zoning category created for unused land the state took for the highway. The state sold the land to Kaempfer.

Kaempfer proposed giving the wedge-shaped parcel to the county along with a lot it owns next to the McDonald's restaurant on N. 19th Street, between N. Lynn and N. Moore streets. That parcel already is zoned for high-rises.

Kirkbride said Kaempfer's planned 367 parking spaces on five above-ground and three below-ground stories of the office building were not in conformity with the county's parking requirements, and could become "an issue." But, he said, he expected the county would consider the creation of two parks an asset.

Tyers said the firm needed the extra density because the triangular shape of the proposed office site would make it more difficult to develop. He noted that because of Rosslyn's rock foundation, the firm has to build upper-story parking, which would decrease the space available to tenants without the extra building height.