Rerolls are one of the few things that are common to just about every Blood Bowl team. The ability to roll a failed attempt for a second time can be absolutely crucial to your success. As such knowing the best times to use them, when to not use them, what they allow you to attempt and how many to have, are all things worth knowing.
As rerolls usually get used most the time on rolls that will cause a turnover (makes sense right) it obviously comes in handy to have one available when you are going to do something that could leave you in a bad spot if it does fail. Of course having a reroll to hand when you do this doesn’t mean that it won’t fail! So the first thing on your mind when looking to use a reroll should be if you can get away without using it up.
For example, if the ball landed deep in your half from the kick off, you are against a slow team that can’t get there and you failed to pick the ball up. This is a situation that comes up a lot, especially for AG3 teams who don’t have a Sure Hands player yet. I hate using a reroll on the first turn, and if the opposing team is in no position to threaten the ball, you can get away with just trying to pick the ball up next turn. Or perhaps you did a one dice block with somebody who was marked up and both players are away from the action. You roll a skull and rather than spending a reroll on it, you just let your player get thumped. Not using rerolls in these situations can be a life saver later on in the half when you really could have done with one.
The other related side of reroll preservation is to not do things that may end up costing you a reroll to avoid a turnover. The aforementioned one dice block, if your player doesn’t have block he will cause a turnover a third of the time. This is a great way to burn through your rerolls quickly and is a mistake often made by players new to the game. Other common causes are taking needlessly risky dodges and go for its. Also it is good practice to not use a reroll on push back results on blocks, on occasion it may be beneficial to do so (especially if you have a lot of rerolls). A push result won’t cause you a turnover but if you reroll it, there is always that risk that you not only wasted a reroll on something that was safe, but you caused a turnover and your player is also now at least prone, if not dead! The opposition can just run off now without needing to dodge or block your player away and some teams may take the opportunity to foul the prone guy as well.