Hi,
I have tested to use the experimental openmsx package but the compilation fail. So here is some steps to do this by hand:

Download openmsx http://downloads.sourceforge.net/openmsx/openmsx-0.11.0.tar.gz (source code)
scp the file in pi@retropie:/home/pi/RetroPie-Setup/tmp/build

cd /home/pi/RetroPie-Setup/tmp/build
sudo tar -xzvf /home/pi/openmsx-0.11.0.tar.gz
cd openmsx-0.11.0

__swapdir=/tmp
swapfile=”$__swapdir/swap”
memory=$(free -t -m | awk ‘/^Total:/{print $2}’)
needed=512
size=$((memory – needed))
mkdir -p “$__swapdir/”
fallocate -l ${size}M “$swapfile”
sudo mkswap “$swapfile”
md_inst=/opt/retropie/emulators/openmsx/

sed -i “s|INSTALL_BASE:=/opt/openMSX|INSTALL_BASE:=$md_inst|” build/custom.mk
sed -i “s|SYMLINK_FOR_BINARY:=true|SYMLINK_FOR_BINARY:=false|” build/custom.mk
make
sudo make install

wget “http://downloads.petrockblock.com/retropiearchives/openmsxroms.zip”
mkdir -p “$md_inst/share/systemroms/”
sudo unzip openmsxroms.zip -d “$md_inst/share/systemroms/”

sudo swapoff “$swapfile” 2>/dev/null
sudo rm -f “$swapfile”

vi /opt/retropie/configs/msx/emulators.cfg

* Add the line: openmsx=”/opt/retropie/emulators/openmsx/bin/openmsx -cart %ROM%”
* Modify: default=”openmsx”

This works. Now I am a little stuck with the configuration of openmsx for using different roms and use disks. I try to use the inside shell but I still have to understand how it works…