Spacing with Font Roboto

[Karl Berry]

    \setmainfont{roboto}

FWIW, as suggested to me by Bob Tennent (roboto package maintainer),
if I change that line to
\usepackage{roboto}

I get non-spacey output:

$ lualatex r.tex
..
$ pdftotext r.pdf -
This is a test. 1

I did get the same spacey output as you reported with the original input.

Looking at roboto.sty, it's unclear to me why it would make a
difference. I surmise different fonts are being loaded. Without knowing
exactly which fonts are being used, ideally through filename lookups
instead of going through the system, I'm not sure there's any way to get
to the bottom of it. --best, karl.