Did a quick google, didn't find anything bad about it. In fact there's a rat store, http://www.ratwarehouse.com they have a beetroot treat for small animals.
I'm not sure if it should be cooked. I imagine, if you would eat it raw, so can the rats. Do people eat that raw? I'm not familiar with beetroot.
It is quite common as a edible vegetable. you can use the leaves in salads and eat the root like a potato, boil it and eat it. I even found some recipes for it. http://vegbox-recipes.co.uk/ingredients/beetroot.php Apparently it is quite tasty :thumbup:
Foods to Feed with Caution
carbonated beveragesârats canât burp (but they can fart!)
Dried corn can contain high levels of fungal contaminates which has been shown to cause liver cancer in rats. Corn also contains high levels of both nitrates and amines. These two compounds can combine in the stomach to form nitrosamines which are carcinogenic. Other foods high in nitrates include beets, celery, eggplant, lettuce, cucumber, radishes, spinach, collards and turnip greens. Therefore, I suggest you limit the amount of these foods in your ratâs diet. Some fresh corn is fine, but if you feed your rats blocks, try to avoid brands which have corn as the first ingredient.