Reroll is a mechanic in the Bakugan Battle Planet game/TCG introduced in the second card set, Bakugan Resurgence. Rerolling allows the player to reroll their Bakugan should they miss or choose to aim for a different BakuCore.
Several Evolved Bakugan have the effect to Reroll once per turn (alongside a second effect) if you miss a roll with it. some Bakugan have this ability on their Character Card, but Ventus Maximus Webam Ultra is the only (Evolved) Bakugan so far that has the ability to reroll as many times if you miss a roll with it.
Some Action Cards have the effect of Reroll, but some cards such as Rip Tide and Second Strike require you to reroll rather than having the option to, but this typically has a second part to the effect. For example, Nature's Blessing is a 5 Energy cost Ventus Action Card that requires you to reroll your Bakugan, but if you open - your Bakugan gets +10 and + .
Although risky and not a good strategy, a player could use an Action Card like Quickfire or Solar Powered to try to collect a different BakuCore, this can be useful for Bakugan and Evolved Bakugan that have an effect that requires you to collect a certain BakuCore. One could use this card to their advantage and reroll Ventus Fangzor Ultra if they did not land on a or BakuCore which would give that Bakugan a +600 and 6 bonus.