Not sure about hibiscus...but you might try cutting the sides of the pot (plastic?) all around and then lowering it into a larger pot. The roots will find their way.
Anthurium flowers get larger with age, if they aren't a cultivar that is supposed to be small flowered. I just cut the top off with 2 or 3 roots and stick it in the pot/ground. The original stalk will sprout again.
