That Ruger, should have a 1-10 twist rate. It should stabilise the heavier bullets just fine. Reloader 17 is to fast for heavy bullet performance. It should be ok for 100 grains and less.
Many rifles chambered in 257 Roberts, have long throats. I'm not familiar with the Ruger offering so I don't know what your chamber is like.
Most of the loads shown in manuals, are kept below 45,000psi, in deference to the older rifles built on early style Mauser actions. Your Ruger should be able to handle a bit more pressure.
I had a Win Mod 70 FTW that wouldn't shoot anything heavier than 100gr, flat based bullets but, it had a twist rate of 1-14. It really loved the 87gr bullets.
I have an acquaintance with a Ruger #1 in 257Rob. His rifle has a 1-10 twist and it handles the heavy bullets quite well. He is an acquaintance because I'm a Conservative and he is a rabid Liberal. It's to much of a hurdle for him, like many LPC supporters.
I have a custom rifle built by a long deceased and missed friend with a 1-12 twist rate. Another friend, bought one of Ian Robertson's stocks, finished it to a Winchester FTW profile and even copied the checkering. Put on a Winchester butt plate and at first glance it looks like it came directly from Winchester. On closer inspection, the fit and finish far surpasses anything off the shelf. 100gr flat base bullets are the heaviest it will shoot.
I'm wandering here, back on topic.
I will give you two suggestions, stick with slower powders, even for the lighter bullets. Varget is a good place to start, if you're going to shoot heavy bullets, go to Re22, W760 or H4831 or powders in those burning rates. If you're going for higher velocities and there isn't any reason not to, make sure your components can handle the higher pressures etc. For instance, I would only purchase +P brass for that rifle because it is of heavier construction and will handle the heavier loads.
