Problems with italics in other font when using roboto condensed

For unknown reasons, roboto.sty redefines \mddefault to be \mddefault@sf which, with the condensed option is c.

Since fbb doesn't provide the condensed series, you get font substitution.

Here's a fix that also avoids spurious warnings.

\documentclass{scrbook}

\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}

\DeclareFontShape{T1}{cmr}{c}{n}{<->ssub*cmr/m/n}{} % avoid a spurious warning

% first roboto to avoid other spurious warnings
\usepackage[condensed]{roboto}

\usepackage{fbb}

% fix the bad declaration made by roboto
\renewcommand{\seriesdefault}{m}

\begin{document}


Test \textit{text}.

\textsf{Condensed}

\end{document}

roboto forces the series default to condensed — imho a odd choice, if roboto is used only for sans serif —, but fbb doesn't support this series.

\documentclass{scrbook}

%\usepackage[utf8]{inputenc} % unneeded in new systems
\usepackage[T1]{fontenc}
\usepackage{fbb}
\usepackage[condensed]{roboto}

\makeatletter
\renewcommand\seriesdefault{\mddefault\@empty}
\makeatother
\begin{document}

Test \textit{text} \sffamily Text \textit{text}

\end{document}