Hades has total control over the (physical) rules of the underworld[1]. Hades can make the stone roll back for arbitrary reasons. But keeping hope alive in Sisyphus is the harder problem. Hades can essentially force Sisyphus to keep trying by making it arbitrarily painful to stop trying, but then hope is no longer his motivation. Hades could reset Sisyphus' memory such that hope remains, but then this loses the profundity of an eternal punishment.
The more interesting case is that Sisyphus can contemplate the nature of the system, and reason toward an out that involved undermining Hades power over the Underworld. If he could pause and do experiments, discover the limits of the enchantment, and work around them, that would be ideal. However such an option would also be an excellent way for Hades to extend and deepen the severity of the punishment. A god's arbitrary power is arbitrarily powerful, after all.
The more interesting case is that Sisyphus can contemplate the nature of the system, and reason toward an out that involved undermining Hades power over the Underworld. If he could pause and do experiments, discover the limits of the enchantment, and work around them, that would be ideal. However such an option would also be an excellent way for Hades to extend and deepen the severity of the punishment. A god's arbitrary power is arbitrarily powerful, after all.
1 - https://en.wikipedia.org/wiki/Sisyphus