These are the T-Rex Boulders, minus a sweet cave c...
If it's hot outside it'll be hot at these rocks, but there are no issues with the area and it is only a little jaunt from Rock Springs (5.3 miles). The rocks are hard to miss if you know what you are looking for and the quality is great.
Stop at Cruel Jack's on I-80 and take 191 south for 5.3 miles. Find a little two-track meandering toward the right and you will see the boulders.