We don't get a physical description of Mrs. Radley, except to learn she would come out to the edge of the porch and "pour water on her cannas." Interestingly, the text doesn't say she waters her flowers, but pours water on them, a more distant and less loving act, as if she does it indifferently.

We do get more description of Mr. Radley, who Scout sees walking to and from work each day before he eventually dies, and she describes him in unpleasant terms, especially his colorless eyes:

He was a thin leathery man with colorless eyes, so colorless they did not reflect light. His cheekbones were sharp and his mouth was wide, with a thin upper lip and a full lower lip. Miss Stephanie Crawford said he was so upright he took the word of God as his only law, and we believed her, because Mr. Radley’s posture was ramrod straight.

The most notable characteristic of the Radleys in the eyes of the town is their lack of sociality. They keep strictly to themselves, an unforgivable sin. They don't go to church like the others and deliberately don't have screen doors, so that their doors can't be kept open on Sunday for people to stop in and say hello. They don't mix with the local community. After Boo gets into trouble, the Radleys take him home and make him equally reclusive. We learn, too, that Mr. Radley's word is respected: he does what he says he will. When Jem speculates that the Radleys keep Boo chained in the basement, Atticus responds that there are other ways to make a person "a ghost," suggesting that the Radleys' hold over their son is psychological rather than physical. The Radleys come across as cold, rigid, and reclusive people willing to sacrifice their son's happiness.

Since none of the characters ever speak with the Radley's directly, it's only assumption that we can go on.  Since the Radley's are "Foot Washin' Baptists" that means that "anything pleasurable is a sin."  They do not go out much, they forbid their son to go out because of his mistakes in his youth, and the only person ever seen out is Mr. Radley.  He is only seen coming back with a bag of groceries once in a while.  After that, the only time they were seen leaving was when they were taken away in death.