I don't get it. Aside from the block capitals, they are pretty distinguishable. Roboto's verticals are generally thicker. The round letters are taller and less round. Roboto has a bit of a curve on the long lines, for example at the bottom of the W. Helvetica's straight lines are actually straight. Roboto has trapezoidal stems on qrpgdb, and the curved lines on those letters get a lot thinner near the vertical. The k has a horizontal bar. The ascenders on lowercase letters are taller than capital letters, but Helvetica keeps them the same height.<p>Edit: of course this doesn't even account for kerning, punctuation, etc.