From A Wiki of Ice and Fire
One of them can be found in the general area between Norvos and Qohor in the Free Cities. Another one connects Volantis to Meereen, going east from Volantis, but it is such a dangerous way that it is commonly known as the demon road.
A Dance with Dragons
At the start of his journey to Volantis Tyrion Lannister takes the opportunity to have a closer look at the Valyrian road that he and Illyrio are traveling on. It runs as straight as a spear to the horizon. It is a ribbon of fused stone raised half a foot above the ground to allow rainfall and snowmelt to run off its shoulders.
Tyrion muses that unlike the muddy tracks that pass for roads in the Seven Kingdoms, the Valyrian roads are wide enough for three wagons to pass abreast, and neither time nor traffic mar them. They still endure, unchanging, four centuries after Valyria itself had met its Doom.