It may not need waterproofing. If its just a little bit of water. Revamping your gutters may do the trick. Stand on the side of the house that the water is coming in, and simply look for low points in the yard, around the house, are your gutters dropping water at least 4′ from the house? Are the gutters clogged?
Is there a hill that runs water towards your house? The solution of excavating can be expensive. I wouldn’t recommend waterproofing from the inside, because the water is still coming in the walls, you then need to install a pump to pump it back out. If that bedroom is in the basement.
If that bedroom is on a first floor or second floor. You will need to look at the fascia, this is behind the gutter. Make sure the drip edge under the shingles overlaps the fascia and gutter
Also look at and roof valleys, chimney and dormers above that bedroom, make sure water cannot penetrate the roofing.
Unfortunately I have not made it to Denver CO to collect business cards yet from local professionals. If you were in Iowa or Illinois I could take care of you.
Hope this helps.