I know this is kinda belated, but on August 18th 2015, the voice of Rafiki in The Lion King, The Lion King 2: Simba's Pride, and The Lion King 1 1\2, was interviewed on a talk show called The Tiara Talk Show.
He talks about quite a few things, including the fact that he thought was going to be voicing Mufasa, and how he came up with Rafiki's voice.
The Lion King was the main focus of the interview, but Simba's Pride was touched upon a little bit:
Interviewer: But you revisited Rafiki for a second time in Lion King 2. And Rafiki gets his own song, which is actually one of my favorites, which is Upendi, about falling in love.
Robert Guillaume: Yeah well, it's always for me to record some singing, cause it was my first love.
Also not to mention at the opening of the video they even play Upendi.
The only reason I found this video was due to a tweet reblogged by Kovu's voice actor Jason Marsden:
It's a nice listen if you love The Lion King, and it'll give you something to listen to while you wait for The Lion Guard in November.