It's not in the Antietam National Military Park's boundaries. It is under a mile from The Burnside/Rohrbach Bridge and about a mile from Snavely's Ford.
Though there appears to be no wartime or postwar photograph of the house, Henry Rohrbach's farm house and barn can be viewed today only with the permission of the resident. It certainly helps to have an Antietam Licensed Battlefield Guide in charge of the expedition. The driveway is somewhat long, arduous for a vehicle and unsigned on the The Burnside Bridge Road. It's location is not shown or described on the National Park Service's Antietam website. But it is there.
Note the HR on the side of the barn. The initials were made by leaving bricks out of the wall, just like the louvers that provided ventilation to avoid the combustion of the loose hay in the mow.
Dave Petruzzi, author of the Complete Gettysburg Guide, negotiated a tour with Antietam NPS historian Ted Alexander; Petruzzi is working on the Complete Antietam Guide. As these photographs show the farm is not being used for agricultural purposes; the house/headquarters is vacant and a small modern dwelling is used by the resident. CWL's guide for Antietam was Justin Mayhue who suggested that Save Historic Antietam and the Civil Preservation Trust are aware that the farm and the other farms around it may sometime come on the market.
CWL and a buddy have been walking the Antietam battlefield four times this year and guided three times by Stephen Recker and once by Justin Mayhue. CWL highly recommends these two gentlemen for your visit. For our fourth visit we requested the Federal approaches to the Rohrbach Bridge including Snavely's Ford, the Confederate defense of the bridge, the Federal advance to the edge of Sharpsburg and the path of A.P. Hill's troops to the battlefield. Mayhue located the Packhorse Ford on the Potomac River and the C&O Canal and Sawmill Road which Hill used come to the battlefield. Everything was right about the day: the November sunshine, comfortable temperatures and new paths on the Antietam Campaign trail.