I've never tried either of those but I quite fancy trying a Roja kit at some point.
I've brewed the Kenridge classic Cabernet/Shiraz and I have a Kenridge classic Shiraz maturing at the moment.
The Cabernet/Shiraz I started drinking after a month, very drinkable IMO and quite nice. It's now over 6 months old (maybe even 7 or 8, would need to check my notes) and it's fantastic. I would say it's now at its peak though as while I did notice a lot of change in the first 3 or 4 months, I've not noticed much of a change since. Great news if you want to drink it early-ish. No issues with allowing it to mature for longer though, not noticed any detrimental effects whatsoever.
As with all kits they over-estimate how much you can make with what they have supplied. If you want a great wine the easy way I would hold back to 20L and use bottled water. If you plan to mature in bulk I would move it to your bulk ageing vessel just before fermentation finishes. That way there will be a CO2 blanket to protect the wine and stop it from oxidising.
I ended up ditching the instructions on the 2nd batch. I didn't like the idea of fermenting on oak chips rather than maturing, so I switched that part around. I also didn't bother using any of the fining agents, potassium sorbate or anything like that, natural-ish wine for me :)