Some classical physics.
Using the equation f = Gm/r^2 for
radius r = 1 AU (1.5×10^11 m) and
f = 9.8 m/s2 -> earth's gravity
G = 6.67 × 10-11 m3 / kg s2
You get the mass of the system as m = 3.3 x 10^33 kg.
After some tinkering, the volume of a 10^7 m thick spherical shell of radius 1 AU is:
4/3 * pi * (r(outer)^3 - r(inner)^3)
Suppose r(outer) is (1.5 x 10^11 + 10^7) m and r(inner) is 1.5 x 10^11 m
Volume = around 6.8 x 10^29 m3
Earth's average density is 5500 kg/m3. Taking this as the average density for the sphere, you'd end up with a mass close to the required mass (3.7 x 10^33 kg). I'm not counting the shell weight itself but it will factor for something especially if it is strong enough to take all the problems coming at it, stay hollow and unliquefied with a molten mantle over it.
Theoretical rock shell without unobtanium shell factoring in:
10^7 meters = around 10000 km deep crust which is a pretty deep crust compared to earth's 5-70km and actually bigger than the earth's radius (6,371 km).
With the shell: Depending on the unobtanium density.
If the shell allows a depth of atleast 3000km (depth to the earth's core):
The Dyson sphere may just have plate tectonics of a new kind. If the radioactive material is hot enough to liquefy the underlying rock and the unobtanium is strong enough to withstand this. So we'd then have a crust floating on a basically slippery sphere. Given that only about half the earth's heat is from radioactive decay and the other half from primordial heat during formation, it may well be that who ever made the dyson sphere system just set it up with the right heat balance and didn't have to do any more.
The thing that will differ is the convection cells set up inside Earth's mantle can basically affect the crust and other convection cells planet-wide. For the Dyson's sphere, these cells would be local, changing the crust only close to that cell. Unless there are heating variations that set up mantle currents that can span larger areas of the sphere's surface, you might not find the continents moving as much as they do here. It may well lack the sheer dynamism of a complete-interior planet-wide tectonic system.
You could have igneous processes such as subduction (deep ocean trenches), uplifting (fold mountains), volcanism (islands and island chains) creating land features. You may have metamorphic processes depending on if the depth you choose for the rock shell is enough to generate the heat-pressure needed to compress rock into granite, diamond, etc. You'd still have sedimentary processes acting on the surface depending on whether you have water and how much of the water cycle happens here and/or wind (solar or atmospheric). Given that the sphere is so large, you may even have the effects of nearby planetary disturbances. So yes, theoretically you could have the crust renewing itself though someone would have to set up the system initially.
Given that there is no magnetic field to protect the atmosphere from getting stripped away, it is doubtful if oxygen will ever get generated in quantities enough to withstand getting blown away by super-sonic solar wind. Even if we posit the presence of maybe some super-resistant bacteria/algae/macro-plant-like organism that evolved/got put there.
Take Venus for example (I said Mars earlier but Mars has a lower gravity so it won't serve as an example). Venus doesn't have a magnetic field and does suffer atmospheric loss due to solar wind despite the presence of oxygen ions at that height: https://en.wikipedia.org/wiki/Atmosphere_of_Venus and http://www.scientificamerican.com/article/solar-wind-transforms-venus-into-shape-of-comet/. What happens is the water molecule simply gets carried off into space. There has to be a constant oxygen generating something. Given that some process will have to physically convert something to oxygen and then have it lost out of the system, how long will this oxygen supply source last?
Plus the Dyson sphere will still have an induced magnetosphere if there is an atmosphere, just like Venus, no helping physics. But even this is not a guarantee to mop up cosmic radiation. Any reaching the surface is still harmful to life. Some horror stories: http://futurism.com/6-horrible-consequences-earth-losing-magnetic-field/
Umm, also the reaction 2 H2 + 02 => 2 H20 doesn't just generate water, it generates massive amounts of heat. Where does all that heat go?
I'd just say, the planet itself is okay, the atmosphere may need help.