Integrating the WordPress admin panel with a frontend theme

I am building a WordPress membership site where I need to collect user generated content in form of:
-posts
-events
-classified ads

I am using three plugins to accomplish this. However I need to integrate the style of the admin panel with the design of the site for certain user roles.

Is this possible without having to build a custom plugin?

To override the CSS on the admin side (in order to make it match your theme) you can enqueue your own css:

function admin_custom_css()
     { wp_enqueue_style( 'stylesheet_name', 'stylesheet.css') };
add_action('admin_enqueue_scripts', 'admin_custom_css' );  

This will insert your custom css on every admin page. See this answer for how to do this for certain admin pages only:

How do I enqueue styles/scripts on certain /wp-admin pages?