If you use mod_rails (i.e. Passenger), you shouldn't have a problem at all. A passenger can place any application on the rack, and I use it to host Sinatra, Padrino and Rails applications on my server. A very simple file is all you need for Sinatra, for example:
require 'sinatra_app'
set :run, false
set :environment, ENV['RACK_ENV'] || 'production'
run Sinatra::Application
config.ru, padrino, :
require ::File.dirname(__FILE__) + '/config/boot.rb'
run Padrino.application
, , , , . Apache vhost Sinatra Padrino , Rails, :
<VirtualHost *:80>
ServerName my.app.com
DocumentRoot "/var/www/apps/myapp/current/public"
RackEnv production
</VirtualHost>
, - , RackEnv RailsEnv.