Does anyone know who makes the mini 14 30 round magazines for ruger?

Tapco makes a Polymer 30 round 5.56/223 magazine for the Mini 14 as does Ruger.  Midway USA has both in stock, Ruger mag is $39.50.

https://www.midwayusa.com/product/1116127495

No idea.  I've read that Ruger occasionally changes magazine suppliers, but I've never seen any names given.

The Mini-14 with a 30rd mag isn't as nice as with the 20rd version. With it's compact carbine style, the larger capacity mags just don't balance in the package that well (unlike the ARs with their huge receiver).

Ruger manufactures a lot more than just firearms, I would imagine they have their own magazine facility.

I'm dubious that Ruger manufactures their own magazines.  While not definitive that they don't make any of their own magazines, Ruger factory LCP/LCP II magazines are marked "MADE IN ITALY".  Mec-Gar seems the most likely manufacturer of those.  Obviously Ruger has some comfort level about going with outside suppliers for magazines.  The Mini magazines don't have foreign manufacturer markings.  There has been speculation that ProMag might make them, but that would mean that they're deliberately making crappier Mini magazines under their own brand.