The rollover valve vents the oil tank pressure that builds in the system. The spring tensioned valve is in the closed position by default. Once a lb or so of pressure  build in the tank it overpowers the spring and relieves the pressure in the tank. In the event of a roll over the default closed position keeps oil from draining out of the oil tank. There is moisture present in the vented air when the sled sits out overnight in the cold the moisture droplets can freeze the valve in place. When the sled is started with a frozen valve that tank can build excessive pressure in a matter of seconds. In testing we have seen it climb as high as 55 psi in a few minutes of idling. This excessive pressure in turn can blow out the oil tank rtv gasket seal. 

Starting in 2020 Yamaha added a12v heater to the valve which heats up when key is turned on. The heater does heat up the valve to thaw it out, however it is only effective if you key on for a few minutes before starting the sled. Even knowing this I would forget to give it time and my 21 srx had a leaking oil tank by 600 miles.

The bypass kit vents the oil tank to the valve cover. The valve cover is vented to atmosphere so this ensures that the oil tank is still vented in the event that the roll over valve freezes up. By venting to the valve cover it also keeps oil contained within the engine during a roll over. 

Retail for the kit is $90 and includes 2 new caps, hose and clamps.