In the standard game, 17 roofs, five of which are blank. When the blanks are drawn, they are not placed and removed from the game, leaving 12 that can be placed.
When we play the no luck variant, we remove 5 roofs at random from the initial 17 at the very start of the game. This leaves 12, all of which will be placed, whether numbered or blank.
Another vote for ignoring the blank roofs. There is still luck as to which number you draw, but you don't have a chance of ending up with an empty turn if you draw a dud.