Going from North to South of Rome on the banks of Tevere.
There is a nice bike path from motorway ring to the Olympic stadium with a few well marked crossings.
Through the city you can follow bike path near the road and sometimes you can go down to the river (this path is marked on the map). Be careful: path near the river is often flooded, wet or full of sand.
On the south i went to Ponte della Maglinana, pike path is marked all the way to the motorway ring.