Thomas Shey
Legend
You engage with it the same way you do with a check in D&D, which is to say generally not unless there's some external mechanic that lets you do it (e.g. in D&D you have things like Bardic Inspiration that lets you retroactively mess with a roll). Some games that use Blackjack rolls do have ways of interacting with it – for example, the Troubleshooters (which uses a d100 version) lets you spend 2 Story Points to flip the d100 (read tens as ones and vice versa), but that's not inherent to the Blackjack roll mechanic itself.
Eclipse Phase does this with its Pools, too.