Take the highway Riga - Ventspils (A10) till Ugale. In Ugale at the signpost "Blazma 10" turn to the right and drive ~5km till sign "Rozkalni" on the left side of the road. The road will take You to "Rozkalni".
Travel directions (by public transportation)
With the public transport: Take a bus from Riga International bus station. The bus is for route - Riga Ventspils and drive till the stoppoint "Ugale".