Can I put a PV panel on my roof and run wires into a room to a power resistor to generate heat?
Works (while the sun is shining), but is a very expensive option and not overly efficient. 

Solar PV panels of a remotely affordable price are about 10% efficient in terms of converting sunlight to electricity. Most of the rest of the sun's energy that hits them is converted to heat. 

So, from a sun conversion point of view, direct solar thermal collection is more efficient.

However, for a grid-tied house, you might be better off (as relative prices of PV and thermal systems shift) putting up some grid-tied panels and using the grid they are tied to run a heat pump (depending on climate, a low-tmperature heat pump, which are relatively new on the scene and can operate in air temperatures below 0° F.)

200W is a tiny amount of heat in any case - about 600 BTU/hr.

PV panels tend to have two specified numbers that will be somewhat relevant for choosing a resistor - the open circuit voltage (no current, no power) and the short circuit current (no voltage, no power) - a sophisticated system tries to shoot for the "maximum power point" which is somewhere in the middle. If you are lucky that might also be specified. You are not trying to "match resistance" (whatever you mean by that) - rather you are looking for a resistor that will drop a voltage somewhat less than the open circuit voltage at a current somewhat less than the short circuit current.