Yes, I have heard of them.
But, I'd really like to see you try to back this statement up:
The roller-delayed blowback design is superior in durability and reliability to the gas-operation of other popular rifles such as the AR-15, M1A, and AK-47.
While there is little doubt the G3 has established a reputation for reliability, I have yet to see any proof it is mechanically more reliable than a quality gas gun like the M1A or the AK. The roller lock design is not without its own faults. For example, they tend to run dirty like the AR, and tend to be more violent in operation, which aside from increasing felt recoil for many compared to designs like the FAL and M1A, also increases the tendency for the rifle to tear the head off cases during extraction.
And the regulations imposed on the roller lock rifles offer unique problems to the American consumer. Besides having heavy and gritty triggers often requiring aftermarket trigger jobs, roller lock clones also have modified mag releases that further miff what is already by far the worst ergonomics of any of the popular 7.62mm battle rifles. It can be fixed, but again, the paddle style magazine release conversion requires aftermarket support.
I don't buy the HK thing either. Not everything that glitters HK on the side of it, or claims HK's heritage, is gold. There is little doubt the HK is a decent rifle, but it is not all that. It's still a stamped sheet metal receiver rifle with sights, trigger, and ergonomics all inferior to many other designs. In terms of control placement, I think even the AK is superior. And the AK certainly lacks nothing in terms of reliability to the roller lock rifles. Accuracy and range, esp when compared to the full power 7.62x51, yes. Reliability, no.
I handled several PTR-91s and an original HK91. I found all of them to be underwhelming compared to the FALs and M1As I handled. In the end, I went with an M1A, and have not regretted it. And while that is obviously a personal choice, at least I can back my opinion up instead of making posts that sound more like advertisements with exaggerated hype and false claims I can't back up.