I did a quick search and for those who want to replay Mass Effect 1 and avoid the romances but still want to go through the all dialogue options and not kill off Ashley or Kaidan to ensure you don’t get stuck in a forced romance you can use this guide I found when I played through.
Originally from
http://masseffect.an...ance_altogether “The long explanation. In ME1: Ashley and Kaidan can be turned down during their first personal convo on the Normandy without any negative consequences. For Ash, pick the "you're out of line" option (she'll be talking about giving aliens full access to the ship). This will kill the romance, and you'll have the same convos with her as a FemShep would. For Kaidan, when he's done talking about Jump Zero during his first personal convo, he says he didn't mean to ramble on. Pick the lower right option ("you're right"). He'll apologise, and you'll have the same convos with him as a MaleShep would.
With Liara, you need to see her first personal convo where she says that she'd like to study Shepard. Then during the next convo (which you need to trigger with the top left option), she'll ask whether there's a romance between Shepard and either Ashley or Kaidan. Pick the middle right option ("they're just friends"). She'll then ask if there's an attraction between Shepard and her. Again, pick the MIDDLE right option (Shepard will say "I'm not interested in you in that way, Liara"). This will kill the romance without any adverse effects. It's important to pick the middle option, because the lower right one has been reported as bugged”
Hope it helped.