The best online reference for Papal heraldry is Roberto Piperno, whose site is based on photographs of Roman monuments. 

 His picture of the crest of Clement XIII shows the cross, diagonal bars, two crowned towers, and a crowned double-eagle.  No roses. 

 His picture of the crest of Clement XIV shows a monument unfortunately attacked by the elements.  It has a round feature, maybe a ring or the crescent moon at the bottom, three stars across the middle, and something I cannot make out across the top.  It might be two arms with crossed swords, or it might be a large carrot.  It certainly doesn't resemble a bear.