Our problem is Clarke's Third Law, "Any sufficiently advanced technology is indistinguishable from magic." As stated, the only answer that can be given is "yes" because it can always be magically terraformed.
What is the specific (very specific) tech level we're dealing with? Our own? The answer is no. Anything we develop in the next 50 years? The answer is still no.
Given that 95% of our current technology was developed in the last 150 years, what about 150 years from now? Terraformed? No. Populated? Likely! A habitable shell is little more than a permanent space ship. So, the answer is "yes" assuming that anybody wants to or that a good reason exists to do so.
300 years from now? I'm going to say yes, absolutely yes. But how? Prognosticating solutions is a pain in the rumpus. If you think about it, with today's technology we can't accurately and consistently predict tomorrow's weather. Environmentalists have been failing to predict the end of the world since the late 60s (and still can't do it.). My goal here isn't to start a debate over global warming and climate change. Polution sucks, we all know it, and we should be diligently working toward reducing and eliminating it. My point is, science is really good at gathering data and really bad at predicting what that means.
So, you shouldn't get your hopes up over my predictions.
Atmosphere
As Alexander points out in a comment, Ceres doesn't have enough gravity to hold an atmosphere in place. It's a bit distant from the sun, too, so even if there were an atmosphere, it's a bit chilly. Let's address these first.
The idea of a Dyson Sphere has been around for a long time. Why not change that to a transparent shell? In fact, let's make it two (if my dual-pane windows are any indication, that's valuable). A bunch of Bussard Ramjets or Ion Thrusters to keep it in place and a station at one of the many connecting points to act as an air lock for shipping and we're good to go.
More futuristically would be a magnetic shell that repels atmospheric atoms and molecules. A "Dyson Swarm" of satellites that generate said shell would be sufficient. Shipping would need appropriately polarized magnetic shielding of their own to cross through the barrier without inducing havoc-generating current throughout their ships' hulls and wiring, but we're dealing with enough magic at this point that it can be done.
Warmth is easy. You need to power your civilization. No matter how you create power, you will always have waste heat. Ceres would have the lowest power bills in the universe due to the vast amount of electricity made available from the many heat-generating stations on the asteroid.
Next, water
Ceres is going to be humid. That's the price of a low gravity. I have no doubt plants will grow on the surface of Ceres, but watering the little green beasties is a whole lot of hurt. You can't simply turn on sprinklers as most of the water will be bouncing off your atmospheric shield. In fact, I can easily imagine drowning the population in an effort to irrigate the vegetation.
Rivers, streams, and ditches don't work, either. At least I have trouble with them. Low G simply plays merry mischief fluids. You'll have trouble just sitting at a cafe and sipping a soda (can you imagine carbonation in a low-G environment? There's an entire Monty Python skit right there!)
So, we're talking about piped water for everything. That'll cost a king's ransom. Not just a drip system for the plants, you need to hydrate the ground. Everywhere. Digging all those 2" wide troughs is inefficient, so we're talking about laying a grid of 2" wide soaker hose everywhere on the surface (where you want plants) and living with the high humidity that will result.
In fact, you'll need condensers to reclaim water from the humidity. But it can be done (300 years from now).
Mowing long-and-weedy plants
I'm only going to touch on plant control, but mowing your lawn will be a pain as plants quickly adapt to the low-G environment. They have heat and possibly enough light (easily solved with a bunch of aesthetically placed artificial sunlamps. We need parks, right?). They have water and we'll assume nutrients (transporting solids, like manure, would have been solved 200 years earlier). But they'll grow long and stingy in the environment. Mowing lawns in a low-G environment might be, well, a bit dangerous.
Behold! the Roomba Mark XX Low-G Lawn Robot! Complete with top-mounted ion thrusters to keep it near the ground and lawn-gobbling plasma surrounding the outer edge to cut the grass!
Finally, comfortable walking
The biggest problem with terraforming Ceres is getting around. Most likely people will be transported everywhere for comfort, but nothing will work better than the good-old magnetic boots!
Which, 300 years from now, will be a natural part of the soles of our shoes, including a bit of nano-computing AI to dynamically adjust the magnetic field strength so that, as we walk, only that part of the sole that should be in contact with the surface of the road, actually is in contact.
And everywhere we walk has some ferrous materials...
Which means that 2" soaker hose is now a 2cm soaker hose and the material it's made out of is magically magnetic (We love you, Arthur!) 'cause we want to stroll in the grassy wilderness of Ceres!
As you can imagine, I've only touched on a fraction of 1% of the problem of terraforming Ceres. We don't know how to terraform Earth (but we try!), but it's a fun thought exercise.
