If I make few T1 under one TurboTax online account and mail it are the QR codes printed on the T1 affects or related the returns each to another?

Every income tax return is separate. You need to use the proper Tax year software that you are filing for. Then when you print your return the QR code is for that specific return.

Thank you for choosing TurboTax.

So, I can make another “new return” for my roommate and mail both in separate envelopes?

Yes, that is correct- you can do it for your room mate under your online account- All the questions which will be asked will then be for him in the new income tax return.

Thank  you for choosing TurboTax.