The existing road networks of Irosin provide access to all its rural barangays to the urban center except for Cawayan, a mountain village. The Maharlika Highway is a main road artery linking the municipality to other places in the Philippines. The existing roads are classified into national, provincial, municipal and barangay roads. The national road has a length of 19.37 kilometers stretching from Bolos in the north to Casini in the south and Mapaso in the east. The provincial road in the municipality includes the whole length of the circumferential road that starts at barangay Gulang-Gulang, traversing Gabao, Tongdol, Gumapia, Batang, San Isidro up to Buenavista, and the roads going to Cogon and San Benon at a total length of 9.05 kilometers. All other existing roads, except the national roads within the poblacion, are municipal roads with a total length of 8.59 kilometers. The roads classified as barangay roads have a total length of 59.0 kilometers. These are roads within the built-up areas in all rural barangays.

As to the type of surfacing for paved roads in 2007, 72.7% of the national roads are Portland Cement Concrete Pavement (PCCP) with Asphalt Armoring and cement concrete, and the remaining 27.3% is asphalt. The 17.4% of the provincial roads are concreted, 22.3% asphalt and 60.3% earth-filled, 52.9% of the municipal roads are concrete, 22% have asphalt surfacing and 25.1% have gravel and/or earth surfacing. Only 12.9% of barangay roads are concrete 2.4% have asphalt surfacing while the remaining 84.7% are unpaved with selected barrow and earth surfacing.

There are fifteen 15 bridges in the municipality and majority of which is along the national roads. Eleven bridges are permanent concrete bridges, 3 are spillways reinforced by culverts and 1 has a metal sheet pile running board. The bridges are mostly in good conditions except for the bridge in Gabao with sheet pile running board that is in a state of disrepair. Majority of the bridges has 15 tons load capacity.