Hi, when we brought our first kitten into our home 6 years ago we had to watch very closely for a few weeks as one of the dogs wanted to eat it. Literally, the kittens head was found in the dogs mouth on several occassions.

We didn't let them meet unless we were all in the room together in order to stop this from happening. It took a while, but they lived together, sharing beds, until the cat was killed on the road.
We let the dogs into the living room during the day, put them away into the bedroom for an hour, and let the kitten into the room to play. After an hour the kitten was put into the bedroom and the dogs let through for a sniff. After a few days of this the kitten was let through at the same time, but the dogs were ON LEADS just to make sure that everything was going to be ok. After the initial 'mouth' by the bitch (she was the only one who bothered) where she was told off, the kitten was allowed to jump down and play. They were fine.
Constant vigilance is needed in the beginning. Do you have a friend (a STRONG friend ;) ) who can help holding the Rottie back at first?