Can I install 2 240v baseboard heaters in separate rooms?
Sure.
It's normal for this sort of setup to have a separate thermostat in each room, but there's no need for a different circuit (nor for 10 Ga wire, from what you have specified so far, which could be fed by a 10 or 15A 240V breaker on 14Ga wire, with considerable room for expansion. - If they pull 600 watts each, you need to provision at 125% for a heating load as it's &quot;continuous&quot;, so 3.125 Amps each, so 4 will fit on a 15A breaker and 14Ga wire, 6 on a 20A breaker and 12Ga wire. If 500W, 5 and 7 for the same cases.)
Nor would you need /3 wire for typical 240V baseboard, which don't use neutral - /2 wire with ground is quite adequate and typical for those - be nice and put red tape on the white wire where you connect it, though.