I just went through this for my 19 CX-9 Sig. I needed snow tires for the winter.
While the bolt circle is the same, you also have to be sure the offset matches (I recall the 9 uses 45mm), width is correct for the tires, and the center diameter is the same. Do a search for vehicle wheel info and there's a site that provides you with what you have and you can check out the ones you're considering.
I find this website useful to confirm wheel spec.https://www.wheel-size.com. Most of the time specs for oem wheels outside of wheel diameter are hard to find online (other than to say that they fit a CX-5).
The rim you quoted seems to be for a 2017-2018 CX-5. Based on the website above (and assuming you are in the north american market), a CX-5 of those year would be wearing ether the following wheel in 19 inch:
The first number is the width (7 inch), the second is the diameter (19 inch) and the last one is the offset (45mm)
The CX-9 signature wheels (again assuming american car)
So the offset is the same, which is good and in my experience usually the one that's hard to match. You can see that the CX-9 wheels are larger. The smaller wheel will still fit, but you lose a little bit of contact patch width on the road. Some people say this is better in snow, but on dry and wet pavement this will result in a bit less grip, probably not very noticeable though. The change in width does mean that you have to choose your tire size carefully to make sure it is compatible with the rim width and matches the same overall diameter than on your CX-9 wheels.
The only other info that we are missing is the load rating of the wheel (how much weight can the wheel support.) I find that information is almost impossible to find, but I think from a cx-5 to a cx-9 it wouldn't be too much of a risk (as opposed to taking a mazda 3 wheel to fit on a cx-9 for example.)
Bottom line is, I think they would fit but they are a bit narrower so be sure to match the tire size to the cx-9 total wheel+tire diameter.
What youri said...a tricky point is there aren't a lot of 19" sizes. A 245/55-19 is within the 2% outside diameter tolerance that is often stated. The 255/50-20 nominal O.D. is 30.1" The 245 is 29.6" O.D. and OK on a rim width of 7" to 8.5".