I want some nice smelling plants to improve the smell in my room. They should be functional year-round and low maintenance.
Lacking information on lighting, seasons, temperature, room size, and scents required, I'd suggest you just buy some Potpourri with a scent you like, and just renew it when the fragrance has gone. Since the leaves are already dead, you won't need to maintain them apart from replacing them if they start to decompose.
Most plants that grow well indoors aren't especially fragrant, and there aren't any that would be fragrant year round. One option you might consider, though, are forced hyacinth bulbs. They are incredibly fragrant for a week or two, very pretty, and easy to care for once you've done the work of forcing them. If you can but forced hyacinth bulbs, they are no work at all.
To force the bulbs yourself, you basically need to refrigerate the bulbs for 12-14 weeks. After that time is passed, you can take them out and pot them up or put them in a forcing vase. If you put new bulbs in the fridge every 2 weeks and potted a new set up bulbs up every 2 weeks, you could hypothetically have a constant supply of hyacinth bulbs.
I'm not sure this would help much if you have an actual odor problem, but if you want to add a sweet smell to a room it would work.
What you've asked for is planting that scents the air year round, and that isn't possible, regardless of the growing environment in your room. For one thing, 'scented plants' can mean more than one thing - many have fragrant leaves, but the fragrance is only detectable if the leaves are bruised, brushed against or crushed. Then there are fragrant flowering plants, and although, for instance, indoor hyacinths, freesias, jasmine, stephanotis and some lily varieties may well scent the air whilst the flowers are present, the maximum amount of flowering time will be between 2-8 weeks, and only if the conditions are right.
I'm afraid you will have to find another way to deal with the problem.