My name is ***** ***** I’ve been involved professionally with dogs in the health and behavioral fields for over 18 years. It will be my pleasure to work with you today.
You are trying to introduce a very strong willed new intact male dog into a household that already has an intact male dog who is also from a strong willed breed. The spoodle has likely been the dominant dog in the house and not going to be accepting of the rottweiler especially if the rottie is bigger than him. If the rottie had been neutered, then the introduction might have gone better. However, the spoodle is at home on his territory and another intact male is on his territory so he feels like he has to show the rottweiler that it is his home.
The funny thing is that the rottie wouldn't immediately try for the top dog position for at least a short while. He would assume he was visiting for the first few weeks before any altercations would have occurred. However, now the rottie has been attack (grabbing a leg counts as an attack) and the rottie is not going to allow the spoodle to attack him.
The first thing at this point is to get them away from the house. Any introduction should always occur away from both dog's normal territory such as a park neither dog has been to or a house where neither goes to. Let them get used to one another in a neutral area before you bring the new dog home for good. In addition, take slightly damp towels and rub them all over each dog then switch the towels and let each dog sleep with the towel having the other dog's scent on it. It will help them get used to each one's scent making it easier for them to adjust.
Since both male dogs are intact, there will likely be altercations until one dog submits to the other. If one was neutered that would help immensely as the intact male wouldn't find the neutered dog a threat to his position in the dog pack. So if you can neuter the rottie, it will help keep the spoodle the alpha male dog in the household. If you neuter the spoodle it will take a little while for his hormones to be reduced and he may still object to the new intact dog and altercations may still be an issue.
I recommend obedience training for all of the dogs. The following site is helpful in helping owners train their dog. Be sure and click on the link to the page on obedience at the bottom. and links on subsequent pages leading to detailed instructions.
Training works best if you train at least 30 minutes a day (two 15 minute sessions). I would start making your dog work via the Nothing in life is free program (NILF). It is outlined below.
Additional training can also help. Both dogs should be leashed and if one dog even looks at the other dog, a correction should be done. Any sign of aggression including a prolonged look, hair raised on the shoulders, a growl or even a stiff legged walk, should be corrected. A correction is a quick tug of the leash and a firm low toned "NO". Once you have done this couple of times, you should notice the dogs ignoring each other. When that happens, you will want to reward them for the desired behavior. Again, use tasty treats like the hot dog slices. This teaches the dogs that you WILL not tolerate fighting in YOUR pack.
You might also get a basket style muzzle for both of the males. This will help prevent any serious injuries while they are adjusting to one another. Basket style muzzles allow normal breathing and often drinking and eating as well. They do prevent bites. It might give them time to work on the changing pack order while unable to do serious damage. I do strongly recommend neutering one of the males preferably the rottweiler.
I hope this information is helpful to you. If you would like any additional information or have more questions please don’t hesitate to press the reply to expert or continue conversation button so I can address any issues you still have . If you do find this helpful, please take this opportunity to rate my answer positively so I am compensated for my time.