The only local roller lock guys I know of is Brethren Armament.

Give them a call and see if they would just do the fold and weld for you. I had them convert a trigger pack to semi a couple years ago and they were pretty easy to work with.

https://brethrenarms.com/category/firearm-services/

I also have a cetme kit i took on trade years ago that i never finished.

I got stuck on the headspacing part...
And i actually bought a serialized reciever, and all of the required compliance parts that was missing from the kit i took on...

I have a welder that has done many odd jobs for me, he said at one time he would help me with the project, however the creating/welding of a receiver I'm not comfortable with asking him to do.

Once the receiver has been completed, i think he would be ok to weld it to the trunion...

Eta: the guy is really good, his hobby is rock crawling...
If you want welds that are like a "stack of dimes", he is my go to!

He also welds aluminum, he saved a very large aluminum boat project i had a few years ago...
Also saved my S10 when my front control arm mounts started ripping off of the frame...

I have a good Miller mig machine at my place near Ogden and my son is a very experienced mig and tig welder if you need any help.  He loves gun projects and I'm sure he would be happy to lend a hand.

I'm in roy, i have a flat that the prior owner folded, but not welded.

I also have a shop press that's air powered, media blast cabinet (not harborfreight), and an air system that i set up for painting a car.

Welding is next on the list to learn...