I have serious doubts about what parts of Roberts' story are true or not.
I agree that Mrs Roberts' story may not be entirely accurate..... ( I have doubts about a police car honking ) but on a point that is so elementary as her observation that she saw Lee leaving and he was donning a dark colored jacket, I can't imagine any reason to doubt that.... It's not as if she was making that up.....
Why do you doubt that Mrs Roberts was simply being candid.....
Walt, a witness is either credible or isn't.
When, as in Roberts' case, her employer says she was known to make up things and when other parts of her story, like the police car tale, are at least questionable, you have a witness who lacks sufficient credibility to take her words at face value. Does that mean that she wasn't telling to truth about the jacket? No, it doesn't, but without some sort of corroboration, we will never really know and, because of that alone, I simply can not rely on anything she says.
But there is more. Roberts, an elderly half blind woman, was trying to get the television to work, to watch the 1pm news, and thus has her back turned to the rest of the room. As she was doing that, why would she even pay much attention to Oswald, who only needed 5 seconds or less to cross the living room, behind Roberts' back, to get to the front door. At best, Roberts would not have seen Oswald for more than two seconds before he walked out the door. Just how likely is it that she made a perfect observation of what Oswald was wearing?