Preheat oven to 400°F. Wash beets and trim off greens. Wrap each beet in a piece of foil, creating a packet, and place packets on a foil-lined baking sheet. Roast 45-60 minutes, until easily pierced with a fork.
Let beets cool until easily handled, then peel and slice into ¼-inch rounds, or wedges.
To make pickles
Divide pickling spice among 2 pint jars. Pack sliced beets into jars.
In a small saucepan, combine vinegar, water, sugar, and pickling salt. Bring to a boil, whisking to dissolve sugar and salt.
Pour over beets, filling the jar with ¼-inch headroom. The beets should be completely covered, but you might not use all the brine. Use a chopstick or wooden dowel to remove any air bubbles.
Screw on lid(s) and let cool to room temperature before transferring to the refrigerator.
To can in a water bath
While beets are roasting, fill a canning pot with water and bring to a boil.
After filling jars, place lids and screw on rims to fingertip tight, then lower carefully into canning pot using a jar lifter.
Cover pot and process 20 minutes, then turn off heat and let jars rest 5 minutes. Remove from pot with jar lifter and place on a towel-lined surface. Let rest 24 hours before transferring to the pantry.
Notes
Any jars not processed and sealed in a water bath must be stored in the refrigerator.
Let pickle for at least 48 hours before eating for best flavor.