First the Ruger Blackhawk is one of the "strongest" actions around. That means you can use +P+ loads in your 357 Mag, if you want to.
Many reloading manuals have special sections devoted to loading Rugers and TC Contenders to much higher pressure levels than other similar 357 Mag firearms. The Ruger Blackhawk also has a "long" cylinder. This gives you some real options on loading very heavy bullets.
I load my own. I like heavy bullets in my 357 Mag. I like to use both Honady 180 grain XTP and Remington 180 grain semi-JHP bullets. I also like Speer 200 grain Total Metal Jacket Silhouette bullets.
Then if you are a traditionalist there is nothing like a Keith SWC cast lead bullet of about 171 grains. For heavy defensive or hunting bullets, I prefer a nice amount of Alliant 2400 powder.
If you are not into handloding and want some "magnum +P" heavy loads, you can go to the Buffalo Bore bullet company website and check out some of there stuff. They point out that some of it is comparable to 30-30 rounds in terms of energy. That has to make a person think a minute.
http://www.buffalobore.com/The Ruger 357 Mag Blackhawk is a really great revolver. I have two one in SS with a red dot mounted on it and another in blue just like it came from the factory, with one exception. Both have target grips, which are more like my 357 Mag Taurus double action in feel.
The Taurus is nice, but there is no way I would put the kind of handloads I regularly use in my Blackhawks into that Taurus.
Enjoy your Ruger Blackhawk! Also experience a few "magnum" rounds as your revolver is up to it!