The source of the Roannay lies north of Francorchamps. It quickly becomes a confined, wooded and sparsely inhabited valley. Then, the valley takes on a more bucolic aspect and the pastures replace the forest areas. It offers numerous views to delight hikers. The Roannay then crosses the hamlets of Ruy and Moulin du Ruy before finishing its 11 kilometres course of on the right bank of the Amblève in Roanne-Coo between the Coo waterfall and the village of La Gleize.