KimmiRowell tells me that she has found the records of Roderick travelling to South Africa on the 'Grandtully Castle' in 1883, single, policeman.
As he was unmarried in 1883, (unless he was being untruthful) he was in the UK and unmarried in 1881 when the census was taken. That hugely reduces the number of possible candidates.
I’ve had a quick look at the FindMyPast transcription of the 1881 census, and there are 19 Roderick Mclennans and 4 Roderick Maclennans listed aged 21 to 31.
There is a police constable, aged 27, unmarried, born Dingwall, Ross and Cromarty, lodging in Glasgow in the household of Roderick McLeod, police constable, 28, married, born Ross and Cromarty, parish unspecified. So the obvious resource to target is the records of Glasgow City Police – see
https://www.glasgowfamilyhistory.org.uk/ExploreRecords/Pages/Police-Officers.aspxIt’s tempting to think that he must be the son of Kenneth Maclennan and Elizabeth (Betsy) Ross, who were living at Burnside, Dingwall, in 1851:
Kenneth McLennan, head, married, 50, stone dyker, born Contin
Betsy McLennan, wife married, 49, born Munlochy
Roderick McLennan, son, 8, scholar, born Dingwall
Elizabeth Fraser, visitor, unmarried, 40, dressmaker, born Inverness-shire
Kenneth McLennan, son, 4, born Dingwall
But in that case, if he is yours, why did he not name any of his sons Kenneth or his daughters Elizabeth or Betsy?
There's another Roderick McLennan police officer, 29, born Fodderty, in South Leith. However he is married to Helen Wilson with two sons, Kenneth (6) and John (1). I can't find them in 1891, but I can't find a death of Helen Wilson or M(a)clennan in Scotland, so it may be that the whole family emigrated together.
I'll have a look at some of the other unmarried ones in the 1881 census.