What if you struggling on bumpy roads to set a good corner speed. There are a number of things to think about here. Most important is probably how you are controlling and interacting with the bike itself. Most riders, cornering, immediately tense up and grip the bars tighter, which partially locks the elbows.
Unfortunately, this means all the pitching, twitching and weaving is passed through to the upper body, from where it's transmitted to the seat and feet, creating a feedback loop and making the rider feel even more insecure, so they grips even tighter.....
For the bike to remain stable in a bumpy turn the suspension, steering and chassis have to be allowed to work effectively. This means making the lightest inputs possible to turn the bike. If you hit a bump mid-corner, the forks will extend or compress, changing the steering geometry slightly, but the bike will compensate, if you let it, with a small twisting action about the headstock.Moments later the rear wheel will hit the same bump, but as it's following the front end it gets a better deal. If there's no rider input and the suspension is set up properly, it should cope.
However, if your arms are tense, preventing the steering twisting around the headstock as it wants to, the bike will change its intended radius and generally feel like it wants to sit up mid-corner. The natural thing to want to do then is grip harder and try to force the bike back onto the tighter line, but the excessive grip will spoil your feel and is also likely to induce unintended throttle changes, both of which only exacerbate the problem.
The answer can be as simple as just to remain relaxed and that starts at the first contact point, the grip at the bars. If the grip is quite loose and the elbows have a good bend in them the arms can act a bit like shock absorbers and dampen or take out the forces before they reach the upper body.
With a relaxed grip there will also less chance of unintended throttle variation over the bumps. It can sometimes be worth sacrificing what may be the best road position for forward visibility or the radii of the corner since particularly bumpy sections of road are often created by the over-use of large heavy goods vehicles. Naturally these bumps follow the tracks of the vehicles tires, so repositioning more centrally in the lane may be an advantage due to the road being subject to less severe damage.