Stick the Roadtec01 SE is a completely new tire...On the sides they look like slicks...Hopefully out in GS sizes soon...How do you like the Road Attak 3 you just put on compared to the Trail Attak 3 you rode before ? I need new tires but can't decide because I liked them equally well !
Road attack were not as good as the TA3 as they were lazy and to be honest the grip was similar but the TA 3 allowed you to push harder as the feed back was and is better and allows you to totally concentrate on the next corner rather than battling with the present corner , if you see what i mean. As for the RoadTech the new tyre looks similar to the old one and the front still has that squimy look to it , if its totally differnt when they bring it out i may try as set but i will have to convince myself first . Photo take 2018 May.
The new ( again when out ) M9rr Trail looks like it could be good but the front may wear quick as the weight of the GS in hard braking can wear the front fast as the wear markers as its more road will be shallow compared to the the Trail CTa3 for example , worth a go tho.
Try the TA3 , great tyre , unflappable as is the GS is , so a great match.

But the RA3 I ran last year and the PST2 2 years ago so I just wanted you to refresh my memories.I even think that I pretty much got the same mileage out of all 3.I ran the Metzeler Roadtec01 on my aircooled R1200GS when they came out new years ago.I liked them as much as the PST2 except in town when I felt some squirm and noise coming from the front but the new ones with the slick like sides look promising....I don't want to be greedy M9RR in GS sizes would be a dream but Roadtec01SE would be worth trying on the GS,too ! Until then I run the TA3 which I like a lot but I thought wit the additional tread debt over the RA3 they would last a little longer...Otherwise can't go wrong with either Continental or Metzeler/Pirelli which are probably the best tire brands right now ! Especially in GS sizes...