Roast the jalapenos in a skillet or over an open flame until the skin is blackened and charred. Wrap in damp paper towels, and set aside until cool enough to handle.
Once cooled, remove the skin of each pepper by rubbing with dry paper towels. Use a vegetable peeler or paring knife to remove extra stubborn pieces. Remove the stems and slice each in half to remove the seeds and ribs. Place the peppers, 1 cup of the lime juice and the horseradish into a blender, and then blend until smooth. In an extra-large pitcher or beverage dispenser, stir the pepper mix, the remaining 1 cup lime juice and the tomato juice until well combined. Refrigerate until ready to use.
To serve, pour 1/2 cup drink mix and 1 1/2 cups (or one 12-ounce can) beer over ice.