Hmm. Dont forget to give Ozzy lots and lots of love and attention. He is probably all nose out of joint at the new addition as it is and then seeing all the attention the newbie is getting, well sometimes they dont take it that well! Give it some time. Ozzy will probably learn to at least tolerate Roxy in a bit as long as his routine of love and affection is not too disrupted. I just introduced a kitten to my cat (although the older cat is only 2.5 years old) and I had to confine the kitten. He cried for a bit at times (I went in and gave him lots of love often though!) but did entertain himself endlessly with balls and stuff.
All I can suggest is lots of love and patience for both and dont punish the older cat for being grumpy. That doesnt help with the resentment either. If there is growling just remove him from the situation and give him lots of love!
Just my
