Beware: Most cheap SSRs purchased from suppliers other than major distributors and authorized resellers are fake with at best a small fraction of the nominal current rating. Either buy the real deal from a supplier that offers traceability back to Crydom or figure out some other way of doing the job.
As Benta has pointed out, the stall current of a universal motor can be extremely high, only limited by winding and circuit resistance, and as the stall current is the current with the rotor locked, i.e. not moving, it draws the same peak inrush current at startup. An order of magnitude higher than the loaded running current is not unusual. You need to be certain the SSR is rated for a high enough surge current for long enough to get your rollers up to speed, and if you want it to survive in the event of a fault, you need either rapid over-current detection to cut the drive signal within a cycle (complicated by the startup surge, so it needs some sort of variable threshold with a decay curve matched to the SSR's surge rating curve) or a massively overrated SSR that can handle the full fault current till the fuse or breaker trips.
Then there's the safety aspect - A SSR is *NOT* an isolator and cannot be trusted to break the circuit in any application that needs (or rather: that should have) an E-stop button, so you'd still need a real electromechanical contactor in series with it. The only advantage of the SSR in that case is (with a smart enough control system) to allow the contactor to only be switched no load, allowing a significantly lower rating contactor to be used without reliability concerns.
Also, an angle grinder motor is not designed for continuous duty, and wont last in such an application. I wouldn't expect more than 100 hours out of a consumer grade angle grinder in such an application, and considerably less if there is any side loading on its gearbox output shaft. This makes it undesirable to spend a lot on a control system for an essentially disposable motor.
It may be worth looking at salvaged treadmill motors and controllers. Provided the treadmill originally used a chain or belt drive, you can easily change the gear ratio for whatever maximum speed you need, the motor is rated for sustained duty, there's soft start to avoid surges, and all the power control electronics you need is already present.