The Thing on the Roof was completed circa December 1930. Howard sent it to Claytons (Strange Tales) on June 6, 1931, but it was later rejected. It was also sent to Argosy on June 19, 1931, but rejected.

Howard finally re-sent it to Weird Tales on July 16, 1931, and sold it for $40.00 but later said he would have let it go for free, just to see it in print. He was quite fond of it. The story is set in the early 1930s and focuses on the legend surrounding the Temple of the Toad God. Howard’s occult tome, Nameless Cults plays a big part in the story.

Howard told his friend Tevis Clyde Smith in a letter around December 1930 (letter #149) about this story before he had submitted it:

I have a still shorter and better story, The Thing on the Roof, which I have not yet sent Farnsworth and which I may not send him, since he says he is stocked up. But this story is by far the best thing I have ever written and one which I am really inclined to believe approaches real literature, distantly, at least.

In August 1931 (letter #172) he mentions to his friend Tevis Clyde Smith that he had received a letter from Farnsworth Wright regarding the story:

I just got a letter from Farnsworth hinting Tamerlane as a fit subject for an Oriental Story story. He likewise mentioned my The Thing on the Roof which is not only the best story by far that I ever wrote, but which is, in my honest opinion a really first-class weird story judged by any standards. That sounds conceited and probably is; just the same, I hold to it. Several months ago Farnsworth rejected the tale saying it seemed too erudite for the general reader, though he liked it himself. Claytons likewise rejected it, saying the plot was too thin etc. etc. also etc. There was no attempt at plot. Like most real weird stories, it had no plot. Argosy rejected it with the usual stereotype. Then Farnsworth asked to see it again, when he accepted my “The Sowers of the Thunder” for Oriental Stories. In his latest letter he accepted it for $40. Not much money, but in this case I wasn’t really thinking about the money and he could have had the story for nothing, if he’d made me that proposition. I’d have given it to him free, just to get it in print.

#173 To H.P. Lovecraft, ca. Mid to Late-August, after August 16, 1931

I’m surprized to learn that the Claytons rejected your stories. I notice that many of the old Weird Tale writers have found a berth there. The editor rejected a couple of my yarns; he gave no reason for the rejection of one, but he objected to the other on the grounds of thin plot and light action. Later Mr. Wright accepted this yarn for Weird Tales, though he had formerly rejected it.

The "other" here is The Thing on the Roof, the first rejected one is 'The Horror from the Mound'.

Lovecraft seemed to have liked the story and we can read Howard's answer in a letter to him dated March 2, 1932 (letter #193):

I’m glad you liked The Thing on the Roof and appreciate your kind comments about it. I’ll feel greatly complimented to have you allude to Justin Geoffrey and Von Junzt in your work.

Tevis also seemed to have liked the story and Howard briefly mentioned this in a letter to him in March 1932 (letter #195):

Glad you liked the Roof business and the Sowers stuff. I’ve had quite a few praises on the Sowers thing, but don’t know whether they’ll get into the Souk.