The last pic almost looks like RMV, but I don't know that that would cause leaf drop, so I'll guess some strain of Blackspot.

Regarding NewDawn, how close is this planted the the sidewalk? This rose throws huge long canes. Did you pre-wet the peat? It's very hard to rewet if it's allowed to dry or didn't reach the sopping wet stage to begin with IME. It looks like it's too dry and perhaps could use a bit of shade to get established. Three weeks isn't long and this may just be transplant shock. However, I would check the soil moisture with my finger, provide the plant with some shade and then wait. It is probably making roots. When I transplanted a large ND this spring it took forever to "take" and required supplemental watering which she usually doesn't need. Please report back. I look forward to others' opinions. : )

New Dawn will survive. It is in a snit because you took it out of the pot. Roses can grow three sets of leaves before it effects them so New Dawn will replace the dead ones.

The last photo is definitely BS. BS comes in many patterns because rose leaves can be different. Some roses really get a bad doze of the particular BS fungus in a certain area where others simply get a sprinkling of fungal spots. You will have to keep an eye on the rose as the BS may have come from the nursery or it may be in your area.

Note that vaporvac wrote "almost" (looks like RMV).

Any etymologist care to comment on oldrosarian's brilliant "in a snit"?

New Dawn was used to a certain soil mix, plus pots warm a rose's roots. Now the roots will be colder and the soil a different mixture. This combo makes a rose's roots go into a mini shock.

As kendravicnair has admitted, the peat's was not watered. That would be another excuse for the rose to get even with a gardener by dropping it's leaves.

Might be.

Could be aphids or spider mites. Just give them a hard spray of water and then go over it with some denatured alcohol on a cloth. Not a lot. Definitely don't leave that there. Now that I look at that first picture of the dryness could be the result of spider mites which usually appear when it's very dry but I've had them when it's raining a lot as well. They will spread so get rid of them now. Sorry you have this on your new plant but it's easy to get rid of.

In a snit, the less clinical word for being totally unhappy with new location.

My Earth Angel threw a huge tantrum when transplanted .

During that transition you may see weird leaves and creepy crawlers. A good spray of water should help with the creepy crawlers. As your rose settles in and gets a better root system things should improve.

Sure looks like spider mites to me.

Me too

Thank you, Kristine.

Note that I was hoping to learn about the phrase’s etymology.

And when the OP asked “Is this a pest. Could this be the problem”, I received no thanks for providing the answer (much less credit for ingenuity).