Conflict is very important in a romance novel -- and really in any kind of a novel at all. What would the story of Romeo and Juliet be without the family feud? How good would Gone with the Wind have been if Scarlett realized from day one that Ashley wasn't the man for her, and that Rhett was her true love? And even in Toy Story, if Buzz hadn't shown up, and threatened to take Woody's place.... Well, you get the idea. Ah, the interest conflict brings to a story!
What is not conflict?
Fights. Arguments. Misunderstandings.
What is conflict?
There are two kinds of conflict in a story, internal and external. I feel they are both needed to carry most plots.
Internal conflict is something that is set inside your character.
Blair was in love with a cop, and he was killed in the line of duty. Now she finds herself falling in love with one of her late husband's friends, another cop. There is no way she will do that without a fight. The fear of losing him the same way is just too strong. It will cause an internal battle that she will have to fight before she can love him.
External conflict is just like you guessed, something on the outside.
Sam has growing feelings for Linda, but she is rich, from the right side of town, and so are all of her friends. Sam is going to school full time, trying to work, trying to keep up his grades; he can hardly make ends meet. Linda's father is a judge, upper crust, his family line can be traced back to the Mayflower. Sam's family line can be followed back to share croppers, his dad worked in a sawmill once, and died in prison, after Linda's father sent him there--which brings us back to internal conflict. If you have plenty of both in your story, it should help keep your plot clicking along, and your readers turning those pages.