Roofers tore flex duct when installing new vent for bathroom fan

Pics: https://imgur.com/a/nNWrpup

Hello!

I had a new roof installed in Sept and we just got our first snow storm. Noticed a 'stripe' of melted snow on my roof that starts at the vent for my bathroom fan that wasn't happening over the past 2 winters.

Just checked things out and they appear to have torn the end of the flex duct right under the new vent causing all of the exhausted warm amd moist air from my bathroom to vent into the space between 2 roof trusses as seen in the pic.

Full disclosure I am a new home owner and had no idea I should have asked the roofers about this while they were here. This is my first house and am still learning about everything.

Couple of questions

1. how the hell do I fix this when there is no metal collar (prob not the right term) or anything on the bottom of exterior vent where I could connect a new flex duct to? In the pic, it looks like they sandwiched the end of the flex duct under the new vent before securing it to the roof deck.

2. I'm in MN.. is flex duct even the right type of ducting to use for a bathroom exhaust fan venting through a roof?

3. is it normal for roofers to not gaf and not tell me 'hey, we ripped the flex duct to this vent and you should fix it before we button things up?

Apologies if this isn't the proper community for this question. Just trying to figure out how boned I might be and maybe a way I can fix this on my own.

Thank you!