Roll ‘n’ Boost can take your opponent by surprise when you manage to summon a very strong and high level monster like Blue Eyes White Dragon with no tribute. This relies on luck since you have to draw that strong monster and get the dice to 4 or below. If your deck has too many high level monsters, you can get yourself with no monsters to summon at all. You will need extra defense strategies.
Can be used each time your Life Points decrease by 2000. Show 1 monster card in your hand to the opponent and roll the die once. The Level of the monster shown becomes that of the die number until the end of the turn.
It is not commonly used in ranked games because even if you manage to summon a strong monster, it can easily get killed by some trap or other card effects. In general, the skill is not reliable, but works fine.
...Is there even a card other than Extra Gate that cares about the Level of a Fusion Monster in the Extra Deck? (There certainly isn't one that cares about the Level of one in the hand, for obvious reasons.)
Four in Six chance to summon Level 5 and higher monsters without a sacrifice? Sign me up!