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Left to air dry I believe they would curl up.

I would try pressing the leaves. Layer them between several layers of blank newsprint and weight the leaves with some heavy books.

https://www.gardeningknowhow.com/plant-problems/pests/insects/leafroller-damage-control.htm

Possibly it's due to canna leaf rollers. See the article above. Good luck

Leaving the Canna in the ground until the first few light frosts lets the bulbs store as much energy as they can.
If your bulbs dry and store with no issues, you will likely have no issues, perhaps just not as much growth or flowers as if you left them in longer.
We as gardeners are always learning!

https://www.gardeningknowhow.com/ornamental/bulbs/canna/storing-canna-bulbs.htm

Here is an excellent article that will give you some good tips for optimizing the growing conditions for the Canna Lily.

https://www.gardeningknowhow.com/ornamental/bulbs/canna/canna-lily-care.htm

It may be a little too soon to despair - it is not entirely unusual for a canna lily to not bloom during its first year as it may be focusing more energy on its growth than on its blooms. However, insufficient sun and water, poor soil, and overcrowding can be to blame. Barring that, another possibility is a lack of phosphorus, which is responsible for blooming. This can easily be remedied by adding a "bloom booster" fertilizer or some bone meal to the soil.

For more information on the care of canna lilies in containers, please visit the following link:

https://www.gardeningknowhow.com/ornamental/bulbs/canna/planting-cannas-in-pots.htm

Canna bulbs will need a rest and dormancy period.
You would not be able to keep them as a house plant.

Here is a link with more information.
https://www.gardeningknowhow.com/ornamental/bulbs/canna/storing-canna-bulbs.htm