Ok I am very keen to try out these games. I remember reading a review of Star Trail in PC Gamer magazine way back when and dying to play it but I was never able to find a copy in stores. So thank you GoG!
That said, I'm not sure where I should start with this series. My first inclination was to just play Star Trail since it's the one I've always wanted to try. But then part of me thinks I should start at the beginning, and another part of me thinks I will probably not have the time to play all three games, so maybe I should just skip to the third one and play that. Is there a definitive 'best game' in this series? Is there a story that continues through all 3?

You can start with Star Trail. The storys of the three games are not related with each other, you can export characters from the first part to the second and from the second to the third to start with more XP and equipment.
Starting directly with in RoA2 won't make the game much harder since you get an extra encounter when the first two characters are still level 1 and a level up in RoA1 yields 1 less hitpoint than in RoA2.
For RoA3 it will make a big difference if you imported characters from RoA2.

Having only played Blade of Destiny and Startrail, the latter is a stronger game imo and if you indeed only have the time to play one of them, Startrail wouldn't be a bad choice.
However, as kmonster mentioned, you can transfer your party over and it's actually interesting to see, how they evolve during the span of two adventures imo. And if you ask me, while I'd say Startrail is the better game, they're similar enough that you probably enjoy the other as well, if you happen to like one of them. So if it's about starting with the series, the first game is most likely the one to do it with. If you want to only play one game, on the other hand, and then decide if you want to play through the series as a whole, they're somewhat close, but you'd probably get more out of Startrail, since it's usually regarded as the strongest entry and it's the one title you're aching to play.

ok, thanks, that definitely helps. I think I will probably try starting out at the beginning as carrying a party through both games sounds pretty cool.

Be warned though, as far as I remember the graphics of RoA1 are pretty bad, the game is awesome though. Graphics of RoA2 are dated, but they are not bad.

It really doesnt matter in my opinion. I got the third game first and played that to the end and had fun. The game will level youre newly created characters to level 6, so you dont need to export characters. I finished ROM 1 a while ago and exported the characters into ROM 2, and am playing currently that. I want to see how far I can level them up, and how the characters evolve. The cool thing is you can print youre characters out (altough Im not sure the gog version support that, oh well screenshots will do) and use them for youre "The Dark Eye"-pen & paper game. Then it would be important I think to play the game in sequence. You will really grow attached to youre characters then.