Discuss Janie as a romantic hero in Hurston's Their Eyes Were Watching God and one of the romantic heroes of Faulkner’s As I Lay Dying. Explain how these romantic heroes contribute to the meaning of the overall works. What would be a good outline/thesis to go about this prompt?

When using the term "romantic," one means either a figure who is engaged in a love story or one who is on a quest. Because you are asking about Janie in relation to Faulkner's characters, the latter concept seems more appropriate.
Hurston's novel is a bildungsroman, or coming-of-age, novel. Tracing Janie's development from a young girl without a sense of self or a voice, the novel ends with a fully actualized woman who has "been to the horizon" and who has achieved her "pear tree" vision of mutuality. She does this by leaving unfulfilling relationships with Logan and Joe and setting off on a quest with Tea Cake. This quest, like all successful romance quests, involves an eventual return home, with wisdom gained though the journey.
Faulkner's novel also involves a journey, though one that is largely unsuccessful for most of the characters. Somewhat inspired by Homer's Odyssey, this journey to return Addie to her preferred resting place involves similar patterns of desire for fulfillment and obstacles that each character must seek to overcome. A strong parallel to Janie seems hard to make, though one might see the parents—Anse and Addie—both having a successful journey. Addie, though dead, does take revenge on her family, whom she resents, and does end up buried in her home county. Anse does achieve new teeth and a new wife, though at the expense of his children. Neither of these characters experience the growth or self-awareness that Janie does, however.
It does not seem plausible that any of the children in Faulkner's novel gain the kind of wisdom or self-expression anticipated in a quest story, though Faulkner beautifully conveys the inner life and aspirations motivating each. Like Janie and her pear tree vision, each of these characters has a singular quality to their personality that drives them intensely and against all odds.
Both of these novels seem quintessentially American as well, and American literature has a strong romantic element to it. I think a strong thesis statement might address the idea of journey and movement and compare the two works in terms of the quest the characters undertake. I think one might make a case for Faulkner's novel ultimately being a repudiation of the romance quest Hurston presents. Hurston was ultimately a more optimistic writer in terms of opportunities for self-actualization. While Faulkner's novel is actually very funny, it is so in a grim way that traffics in gallows-type humor.