From A Wiki of Ice and Fire
The roseroad splits from the kingsroad just south of King's Landing in the Crownlands. It briefly runs southwest through the edge of the kingswood. The roseroad crosses the Mander at Bitterbridge and again at Highgarden, where it meets the Ocean Road. After Highgarden, it continues southwest to Oldtown at Whispering Sound.
A Clash of Kings
During the War of the Five Kings, Mace Tyrell closes the roseroad to all shipments of food to King's Landing, as he supports Renly Baratheon's claim to the Iron Throne. Renly slowly marches his host down the roseroad from Highgarden towards King's Landing.