Would a Linus Roadster work on an off-road country environment? Would a bicycle like a Linus Roadster Classic handle well on an off-road country environment or would you recommend a mountain bike for this?
The Linus Roadster is not the bike I'd choose for rural poor quality tarmac, gravel roads or packed dirt trails.
The stock 32mm tires do give a bit more volume than standard road size tires to soak up bumps a little (they are about the the same size as cyclo-cross tires ) but they are slicks designed for paved roads. The main problems are the single speed drivetrain and rear wheel only coaster brake. (There's also the fact that the bike screams urban hipster!!!)
You don't need a full-on mountain bike for poor quality tarmac, gravel roads or packed dirt trails as long as they are relatively smooth without big bumps and holes. If you want flat bars a hybrid would work well. You don't need a suspension fork and tires 35-40mm wide with a medium tread pattern will be fine. If you want drop bars gravel bikes are ideal for these sorts or surfaces as well.