Hello! Welcome to the forum.
If you want your guinea pig living in your room, you will need a sleep and a toilet corner for it. A plastic tray will do the trick for the toilet corner. You put some newspaper on and then some hay over it. Clean it out regularly, ideally daily or at least every second day, as it will smell and attract all kinds of insects you (and your guinea pig) will not want in your room! Make sure that the toilet tray is standing somewhere protected, so the guinea pig will want to use it. If wished, put a turned up cardboard box with door openings over it. Roaming guinea pigs will create their own toilet corners - put plastic down where yours will sit regularly, so you can just wipe it and keep your room clean and odourless that way.
Your guinea pig will want a place to sleep and hide as well. You can use another tray, put old newspaper on, then an old towel. As a hide, you can use a carboard box, in which you cut "doors". If you put that on top of the tray, your guinea pig has a very cosy little home! You need to change the newspaper and wash the towel regularly, as it will pee and poo on it and it can get very smelly and disgusting very quickly! Make sure that you either block up your bed or that you can get move it easily for cleaning, as your guinea pig will happily live (and pee and poo) under it!
Make sure that your guinea pigs can't leave the room and that no other animals can get in. Cats, dogs and rats will kill guinea pigs.
Here is a link to a good diet. Guinea pigs eat a LOT of meadow (=grass) hay or grass (NOT straw; that can injure the guinea pigs!) and fresh vegetables. Many Asian vegetables are very expensive here in Britain, so we do not feed them, but pak choi and similar vegetables can be fed. Your guinea pig can live without pellets (it is only about 15% of their diet), but you need to make sure that it gets plenty of vitamin C daily from vitamin C rich vegetables like bell peppers or parsley. You give about one generous cup of vegetables per day (accounting for no pellets). You can give half in the morning and half in the evening. Please make sure that you give a mix of vegetables and herbs, as you don't have pellets.
Here is a list of vegetables they can eat. They CANNOT eat any onion or garlic plants, like spring onions or leeks; or potatoes. They should NOT eat any seeds, because they are fattening. However, you can grow some rice in a tray and feed it before it make seedheads. Rice counts as grass.
http://www.theguineapigforum.co.uk/showthread.php?t=42
Here is a guide for a balanced diet. You will need to adapt it to for your locally available vegetables.
http://www.theguineapigforum.co.uk/showthread.php?t=37030
Thank you for caring for your guinea pig! I hope that you will enjoy it.
PS: Here is some good general information on guinea pigs and a link to the sounds they make.
http://web.onetel.net.uk/~petergurney/preface.html
(Peter Gurney was one of the first vets to specialise in guinea pigs and is still the best source for information)
http://www.jackiesguineapiggies.com/guineapigsounds.html