sure, you can create the package on Linux. You can't do anything with it once it is created, unless you have a Roku to load it onto. Generally speaking, you add
export ROKU_DEV_TARGET=192.168.1.64
(ip of your roku)
to ~/.bash_profile or ~/.bashrc depending on how your system is configured, then reload the environment:
source ~/.bash_profile
then cd into the top of your roku project:
cd simpleposter/
and type:
make install
which should create a zip file of your project in the zips folder of the Roku SDK, and also will push the zip to your roku.
- Joel