Whisk together the vinegar, lemon juice, mustard, garlic, sugar, salt, pepper and oil in a small bowl. Cover and refrigerate for at least 30 minutes before using to allow the flavors to meld.
Just before assembling the sandwiches, place the romaine in a medium bowl and toss with the vinaigrette.
To make the sandwiches:
Combine mayo and blue cheese to taste. Spread on toasted sandwich rolls. Assemble sandwiches however you wish.