This seems to be a myth that has grown up around the case. I just rechecked PR's recorded statements and she also indicates she was in bed first, and JR followed very shortly after. The time she spent getting ready for the trip overlaps with the time JR spent playing with BR. If anyone has any other original sources that say otherwise, please do post them.
From first interview
TT: About what time did you head up to bed that night?
PR: Um, probably around 9:30, 10:00 something like that.
TT: Okay. What time did John go to bed that night? Do you remember hearing him come upstairs at all.
PR: Yeah. I remember him coming to bed. I don’t know what time it was. It was shortly after I came to bed.
from second interview
18 TOM HANEY: When you actually went
19 to sleep?
20 PATSY RAMSEY: Well, it was pretty
21 soon after I hit the bed, yeah, I was pretty
22 tired.
23 TOM HANEY: So about--
24 PATSY RAMSEY: About 10:30-ish, I
25 think.
From Johns first interview
JR: Uh, it was probably 8:30 p.m., quarter to nine when we left as I recall. And uh, we had gift baskets for the Walkers, for the Stines, for the Franks, and we left the White’s and we took a basket to the Walkers; as I recall Patsy went in and I stayed in the car; we drove to the Stines and did the same thing, uh, and debated on whether to go to the Franks or not, but it was getting late and that was a ways away, so we decided to go home. So we probably got home about nineish, nine-fifteen I think, drove in the back through the alley into the garage. Uh JonBenet had fallen fast to sleep. Uh, I carried her inside and took her upstairs and put her in bed, put her on her bed. Uh Patsy came up behind me, and then I went down to get Burke ready for bed, he was down in the living room, working on a toy he got putting it together, and tried to get him to go to bed because we had to get up early the next morning, but he wanted to get this toy put together, so I worked with him on that for 10 15 minutes probably; and then I took him up to bed and got his pajamas on, probably brushed his teeth, and then I went up stairs from there and got ready for bed. I read her a little bit. The lights went out around ten-thirtyish or ten-forty.
TT: John, about what time do you think you fell asleep on Christmas night?
JR: Well I think it was 10:30 p.m. or 10:40 p.m. probably somewhere in that range.
From John's second interview
JOHN RAMSEY: Right. I started to get Burke
22 into bed; get him ready. And he was sitting in the
23 living room working on a toy, an assembly little
24 toy he got for Christmas. And I could see that I
25 was going to get him to go easy. So I sat down and
0115
1 helped him put it together to try to expedite the
2 process. So we did that together and it took us
3 ten or twenty minutes, I guess. And then he went
4 up to bed. And then we went up to bed. And I think
5 we used the front stairs (INAUDIBLE).
6 LOU SMIT: And what time was it that you got
7 (INAUDIBLE)?
8 JOHN RAMSEY: It was probably nineish, 9:15
9 maybe. (INAUDIBLE).
10 LOU SMIT: So you looked for Burke?
11 JOHN RAMSEY: Yeah. Then I got Burke on his
12 way to bed. I guess I must have gotten him for
13 bed, but I don't remember now for sure. But he got
14 in bed, and by the time I got to bed I think Patsy
15 had already been.
16 LOU SMIT: You just go right directly from
17 Burke and came upstairs? Is that what your saying?
18 JOHN RAMSEY: Yeah. I believe so.
So my problem with the story is that John says they return home between 9:00 & 9:15. He carries JB upstairs, plays with Burke for 15 or 20 minutes, takes him upstairs and goes to bed. He states that the lights were out at 10:40. That is as much as an hour and forty minutes after they got home, yet he is only accounting for about 30 minutes of time. This should be a simple period of time and his and Patsy's estimates should be close but there is a huge amount of time missing here relatively speaking.