How should I cleanup after roadkill to prevent dogs from being attracted to the spot?

I love love love and therefore always recommend Natures Miracle. It works amazing getting not only smell and stains out, but to completely remove any trace of potty issues from your surfaces so that your pup can't smell them and try to use the same spot again. I'm not sure how well it would work on blood, but it should at least get rid of the smell that attracts animals to the spot. I second using cat litter to soak it up, but just be cautious that some dogs are attracted to the smell of litter.

I would like to echo the suggestion to apply cat litter to the spot.
If you live in a dry area, the litter should absorb some of the smell, and then be dry enough that you could sweep away the area within a few days/a week to disburse the smell. In the meantime, it may be valuable to keep the dogs on leashes, at least until you pass the are and the smell is no longer a lure. As you sweep away the remnants, it should lesson their interest in it. After it is dry, as was previously mentioned, a douse of white vinegar may get the last of the smell up.
Unfortunately for those of us who hike outside of the city, these kinds of things happen- nature can be a bit brutal. Good luck and enjoy your hikes!

Many pet retail stores sell dog repellents of stain and odor removers such as Nature's Miracle. Honestly though, it's probably not a good idea to add chemicals to a Natural Area, without having it be approved by the most relevant government organization. The chemicals may damage the plants or wildlife in the area.

The best thing you can do it practice "leave it" with your dog, using high value treats. It's important to work them up to more difficult leave-it's such as carcasses. Another, less invasive option, is to simply get some gravel or rocks and stack them onto the affected area, so that your dogs don't have access to roll in it.

I don't have experience with this myself, but perhaps you could try pouring either white vinegar or hydrogen peroxide over the area and letting it sit for 5-10 minutes, then you could pour cat litter over it to soak up the excess liquid.