Searching for "Rosanna" on Soundmondo turns up a performance submitted by Chris Poser. There are no Performance notes - so you'll have to dig around the Performance. Make sure to check PARTs 9-16 because another of Chris's Performances does have notes and mentions using upper PARTs with an external keyboard. Might not be used this way in this Performance - but just something to consider given what you can glean from his other Performances with notes.

Motif XF has been around longer - and Montage/MODX can "do" all of the preset Motif XF stuff - so this is interesting:

https://www.youtube.com/watch?v=fgq0tNLheNQ

Not all of the sounds are spelled out (just the piano sound - which is a preset EQ'd). This may suggest the rest are XF presets too. Both upper and lower are XFs.

There's other stuff out there to listen to. This one shows fairly clearly the splits and times when button presses bring in other sounds - or mod wheel for the lower sometimes for changing the sound. This just gives some ideas of how one may lay out the sounds and MODX has a few more tricks with scenes.

That's a great link. I've got just about everything, just need to figure out that sequenced descending thing. They said it was a Micro Composer.
I had to spread the song across 2 performances to get all the parts.

I've seen different approaches. Some have an arp that covers some of the notes - and the player has to trigger the ARP every quarter note to play the line. Some have the entire part sequenced with a single button press. Some play nearly the entire line and use effects/delay to "double up" on notes.

There's a lot going on - I'd probably arp it or sequence the entire thing for a single button press. You can build the user ARP as fixed note using the Performance Recorder (to "sequence" the entire thing). Or use Org Note for the quarter-note approach (and build less notes into the arppegio). My approach is to slow down the tempo significantly and have the clicks subdivide the beat enough so I can be accurate with the starts and stops. You may want to use the pattern sequencer to use some of the job functions - but I think the old performance recorder way would be fine considering how fast the notes fly by.

Having the tempo slow for entering in the notes allows for accurate entry of fast parts with less retries.

I found a MIDI file where that part sounds pretty close. I'm going to assume I can bring a MIDI file into the MODX and somehow trigger it and put a stereo delay on it.
I have no clue where to start. I haven't even looked at the MODX sequencer yet.

I'm playing all the other parts live so that's the only missing piece. If I can trigger that cascading part with the high C and then go into the portamento synth lead, I think it will sound good.

Does this only apply to drums?
https://www.youtube.com/watch?v=GG882dFpa9o

This kind of thing doesn't only apply to drums - but I wouldn't have done it this way using the pattern feature. I would load a MIDI file into the Performance Recorder (MIDI) and use the ARP conversion features there (MIDI to ARP).

The limitation of using an ARP is you only get 16 unique notes. So something that has a pattern that runs down the keyboard with lots of notes may exceed this limit. Unique notes meaning unique MIDI note values. If you play middle C 16 times - this is only one MIDI note value (repeated 16 times) - so it counts as one UNIQUE midi note value. If the pattern repeats itself but an octave lower - you can save notes of the ARP by only recording the first octave then using ARP features to play the next octave(s) down.

Alternatively ...

Or you could always save a recording as an audio file of this sound playing the entire pattern and assign this whole audio recording to a drum key. Then a one-shot press of a key will play the audio.

With ARP building - start small and experiment with something simple and get that under your belt if you haven't generated ARPs before. Not that you couldn't or shouldn't do this a more automated way. Building ARPs from scratch is usually faster in the long run. Starting from a MID file is fine too but I would trim everything on the computer first so there's only a single track in the MID file and with all the measures/beats before and after the "lick" of interested removed (trimmed).

The MIDI file is trimmed, just a single track. It's 28 notes total, 10 unique notes.

So if I click Rec/Play, then the MIDI tab...where do I go from there?
In the Pattern tab there's an Edit/Job button that gets me to the Load MIDI file option. But in the MIDI tab there isn't.

... just adding that C3 and C2 (two "C"'s an octave apart) count as two unique notes. Not sure how your analysis treated octave notes. There are 128 unique notes total in MIDI of which you can pick any 16 of them to construct an ARP and repeat these 16 unique notes if you want.

Assuming you've counted correctly and are below 16 max, then you can load the MIDI file in the performance recorder (MIDI) then use the conversion to ARP feature. Set the ARP type to Fixed and start with that. Name your ARP so it's easy to find.

Then you would go to the PART with the sound you want this ARP to play and add it to ARP #1's slot. Set loop to off. You can set the trigger so your keypress is toggled instead of gated. This prevents having to hold down the key. You can mute this PART after it's done so you don't inadvertently trigger the ARP later (you'd have to press that same trigger key 3 times to retrigger. First time to trigger on - second to toggle off - third to toggle back on). That's just one way. You have many options. There's not one way.

I think that experimenting with ARPs with easier "throw away" custom ARPs will help paint the picture of how you want to eventually render/program these notes.

But I can't see how to load the MIDI file into the performance recorder.

Reference manual page 54 (paraphrased):

Touch the "Song Name" to bring up the options to load a song or rename the current song.

When you select the "load" function - the next screen you can touch "content type" which will allow for select ".MID file" as an option and this will pull from your USB stick.