No need to go back over Oslo or Stockholm. You will need to take a bus though, from Bodø to Narvik, from where you can take a train to Kiruna. Or partly by Hurtigruten (select the port to port option, not the excursions ! To Harstad, maybe Svolvær, and then continue by bus. Probably the most comfortable option) if you don't want to fly. 

Very scenic journey, whatever option (except flying). 

Don't use the Interrail planner to plan. But use the planner of www.bahn.com which has most up to date timetables of all Europe, or www.entur.no and www.sj.se and www.vr.fi for the national companies Websites. Entur in Norway also includes all buses. 

From Kiruna you take the VY regional train to Luleå. From Luleå to Haparanda you take the Länstrafiken Norrbotten bus, which is included in Interrail/Eurail. From Haparanda bus station you either take a local bus (not included) or walk to the train station in Tornio, see more info in the link below.

https://haparandatornio.com/area-guide/getting-to-haparandatornio/

In Tornio you have access to Finnish trains. 

Don't forget that there is a 1 h time difference between Sweden and Finland.

You have to split the search Kiruna-Rovaniemi in multiple Parts:

Day 1:

Kiruna to Haparanda: change trains in Boden or Luleå

Then walk from Haparanda to Tornio-Itainen across the border (5km, 1h walk).

Tornio-Itainen to Oulu or Kemi: one train late evening, doesn't run daily.

Stay overnight in Kemi or Oulu (alternative: stay in the night train from Tornio and sleep until Tampere, and then take a day train back up to Rovaniemi)

Day 2:

Oulu or Kemi to Rovaniemi: several direct trains per day