What do I add to template.php so I can render regions in a page created in hook_menu()?
Well, replace this line 

render($region['sidebar_left']); 


with 

render(block_get_blocks_by_region('sidebar_left'));


and replace this line

render($region['sidebar_right']);


with

render(block_get_blocks_by_region('sidebar_right'));


hope it will work for your case :)