I have been looking into this company a bit more, I noticed there is very little published about it and some of the info seems a bit incorrect. You commonly see reference that Roberts and Kimball only made rifles for about 1 year. Roberts and Kimball was announced in the American rifle June, 1935 edition as a semi-custom rifle company formed by Ned Roberts of .257 Roberts fame and WGC Kimball of Baker and Kimball a mail order antique firearm dealer and President large sheepskin tannery. Inserted below are some of the period ads


Here we see an advertisement stating they will be going out of business this was published in American rifleman july 1936



In December of 1936
We get a notice that Kimballs 2 firearm companies will be merging into the new "Kimball Arms Company"



The Roberts Target Model and Kimball Sporting Mauser would be advertised in Kimball Arms catalog up in till the Ninth edition circa 1942. I believe this is when the company had finally run out of the 98 actions they had been sourcing from Bayard in Belgium.




As well we commonly see reference to SA Leonard being the stock maker but I think the work was also done by another as well.



I have seen Ned Roberts write about J.E. Morrell doing some target shooting with him one weekend but no other information.



These pictures are both from a "Kimball Arms Company marked rifle


Does anyone else have some more info?

I think it seems like J.E. Morrell is Joseph E. Morrell who I found helped Ned Roberts with early testing of the .257 cartridge

https://archive.org/details/sim_american-rifleman_1931-12_79_12/page/10/mode/2up?q=Morrell