can i roam in the USA for a full year?

No, you cannot.
Here a previous discussion, take a lot of all the possibilities.
https://community.fizz.ca/questions/1928876-snow-bird-coverage

Edited answer
If you want people to reach you through your Canadian phone number while you're in the US I suggest this work around.

Before entering the US do this:

1- Make sure you have a Canada+US plan
2- Buy your self a US provider SIM card
3- Set a call transfer for all your calls on your Fizz number to your new US phone number.
4- Swap the SIM card in your phone for the US SIM card.

Chizz :))

Agree with Chizz. Look into Roam mobility.

No maximum 3 months straight

Buy a USA SIM instead