You can feed dandelion greens, chicory, collard greens, kale, some lettuce (not iceberg because it isn't very nutritious), roses (leaves and flowers, make sure they have not been sprayed with pesticides), mazuri tortoise diet, zoo med grassland tortoise diet (My RT Shorty hasn't taken an interest to it, though) and much more. Remember, variety is key. You can feed bell peppers but I'm not sure if mushrooms are good for Russians. The Weed identifying forum has more information on what weeds are safe to feed tortoises.