Just my .02c. I have kept corn snakes for about 7 years. At one time I bred mice/rats for them but gave that up after several years for multiple reasons, and had to return to buying food. Each snake eats one rat per meal, and each rat costs me close to $4. So, when I ordered the MPC pullet special and three arrived with bung feet (one had a foot that was completely curled backwards, making it unable to walk. It kinda hopped, dragging the crippled foot behind it, and 2 had toes that were bent backward), I watched them for a couple of days but they clearly weren't thriving. They couldn't get enough food due to being unable to compete with the healthier chicks and were getting noticeably weaker. So I weighed their needs (for us to hand feed them) against the needs of my snakes to eat (and unfortunately, attempts to convince snakes to eat vegetarian food are rarely successful), and "culled" the three crippled chicks by providing meals for three of my snakes. The decision was NOT made lightly but I do believe it was a practical decision. The snake had to eat, the chick was dying anyway, and what point is there in "wasting" the life of the chick by throwing it in the trash can or burying it, and then going out and killing a rat to feed to the snake?
For the OP, if your roo chicks are destined to die anyway, why not provide them as meals to an animal that needs to eat. By doing so, you are saving another critter's life.