Paris-Roubaix is different than other races in terms of strategy. It has a much longer final. The number of cobbled sectors seems to high to overlook, but there are really three crucial fases.
Phase 1: Sectors 20-17 (ca. 100 km before the finish)
Here is when the first selection happens, with the dreaded sector 19, Trouée d'Arenberg, as the focal point. There is no othere race where you need to be in the front this early. There will always be crashes and mechanicals, so you need to be in front of those. The first two or three groups after this sector can ride the final, all the rest is out. If you missed the first selection in Arenberg you can use the next two sectors to come back. Important is to have several teammates together in front. The team that manages that can control the race.
Phase 2: Sectors 13-11 (ca. 50 km before the finish)
This is the right place to "make the jump". In other classics it would be too early, but here you can accelerate and close the gap to the breakaway, all the way to the front of the race. After that you're in a luxurious position for the next 20 km. Sector 11, Mons-en-Pévèle, is the crucial one. To have two or more riders from the same team can still be a big tactical advantage.
Phase 3: Sectors 6-4 (ca. 20 km before the finish)
Everybody knows about the importance of sector 4, Carrefour de l'Arbre, but the two just before that are already suitable to launch a decisive attack. After Carrefour there are no more tough sectors. If you have a good sprint you can follow the strongest riders. If you want to finish solo you have to drop them here, or with a surprise attack on the asphalt. After that it's a cruise to the Roubaix velodrome.