As other's mentioned, if you can work on your own Roland's you'll probably be fine working on a Mimaki.
I've been in the same situation as I'm on my own on servicing and went from VP540s (on my third one now) and XC540s and have slowly moved over to Mimaki.
In my experience Roland maintenance, problem solving and part replacement is easier than doing the same procedures on a Mimaki. The Rolands build quality and design just feels more robust and solid and I could tear down a Roland and put it back together without consulting a service manual. That being said Mimaki's are a lot simpler to own and operate. You're usually dealing with only one head so all those head alignments you're always doing on your Roland pretty much disappear. It's frustrating on the Mimaki in that you're often replacing an entire assembly versus a single small part but that also makes things simpler sometimes. I personally had a REALLY hard time following the assembly workflow and just overall workflow of how the Mimaki's operate after coming from the Rolands which were dead simple. It's fine now but I still miss how straightforward the Rolands were.
I'm on my 3rd Mimaki now (JV series printers) and have sort of gotten the hang of it. The main complaints that I've had on the Mimaki's is that I've several issues of a single channel of ink dropping out and it's near impossible to get it back. On the Roland you could just pull ink through that channel but on the Mimaki's you're pulling ink through the whole print head at once (unless you isolate and close off the other color ink lines which is a weird way to do it) and you're going to feel like you're wasting a ton of ink fixing these issues. Both my JV160 and JV300 also had major issues within one week of the warranties expiring. JV300 dropped both heads and the JV160's motherboard died literally the day after my warranty expired.
Mimaki print heads are also proprietary to Mimaki. Yes, it's the same head everyone else uses but there's a software lock that means that you have to buy the Mimaki version of the head so no more scouring the internet and ordering a cheap DX5 from China like you could do on the Rolands. That being said, as I mentioned earlier, it's REALLY nice not having to deal with so many alignments. Just be prepared for sticker shock when you have to replace a dual channel mimaki damper ($100 per damper for oem) or else a print head.
