I have came across the same installation issue with 2.2.1 as mentioned here (hosting server doesnt have php5 installed, but allows use of .php5 appendix)
I have created a .htaccess file with both the following inside:
AddType x-mapp-php5 .php
AddHandler x-mapp-php5 .php
I am presuming when root directory is mentioned that it means the same directory as where SilverStripe is installed, or the public_html of the hosted service?
Unfortunately neither positions, changes the lack of recognition of php5,
so it doesnt allow me to proceed with installation.
Any further tips?