When using pdflscape and fancyhdr, the headers also get rotated. Whilst it's a normal behaviour in most cases (especially when the document has to be printed), I am dealing with a report which will never be printed, so this default behaviour is more annoying.
Here is a MWE of a document dealing with portrait and landscape pages:
\documentclass[a4paper, 10pt]{article}
\usepackage{graphicx}
\usepackage{pdflscape}
\usepackage{fancyhdr}
\usepackage{lipsum}
\usepackage[left=2cm, right=2cm, bottom=2cm, top=2cm]{geometry}
\setlength{\headheight}{32pt}
\lhead{\includegraphics[scale=.5]{tt}\\Foo}
\rhead{\includegraphics[scale=.5]{tt}\\\thepage}
\cfoot{}
\fancypagestyle{customlandscape}{%
\fancyhf{}
\newgeometry{left=1cm, right=1cm, bottom=1cm, top=1cm}
% ??
}
\pagestyle{fancy}
\begin{document}
\lipsum[1-10]
\newpage
\pagestyle{customlandscape}
\begin{landscape}
Here is the landscaped content, the header of this page should look like the rest...
\end{landscape}
\newpage
\pagestyle{plain}
\lipsum[1-10]
\end{document}
Note : you will have to provide 2 images called tt for it to compile, sorry for that. So, if we look a bit closer, the header of the portrait pages look like this :

How can I manage for my landscape pages to look like this ? :

Currently, by compiling my MWE, you'll notice that the header is on the right on the landscape page.
PS : There is another problem in this MWE, after switching back to portrait, it seems I'm not able to restore the default pagestyle (with the images in the header).