DR Jose asked many questions about my pork roast. I will try to answer.I cooked it at 350F. And yes I had a marinade and kept taking it out to baste it. Also (and I'm not sure if this was a factor), but the person I was cooking it for was late. So I took the roast out of the oven completely for like 25 minutes in the middle. Is that very bad?
It was a regular roasting pot (not high edges) and sitting on a metal roasting rack.
Yes, I did take it out of the fridge first, but only for like 20 minutes.
Yes, it was underdone as in raw near the bone. And I don't have an oven thermometer. Is that something I need?
Thanks for your help. I rarely cook roasts. So I figured 1 1/2 hours seemed like plenty of time! 
350 is always a good, safe temp for roasting.
As for basting, it's usually best not to baste until a good 30-40 minutes into the cooking time. You have to make sure that the outside of the meat has cooked/sealed. -Which is part of the reasoning behind starting the roast at a higher temp inititially, and then going "low and slow" after that. I know it was "fashionable" to baste meat every 10-15 minutes, but all that does is prevent the piece of meat and the oven from maintaining a constant temperature. It usually takes anywhere from 5-10 minutes for an oven to come back up to temp after the over door has been opened, so... If you feel you must baste, do it as quick as possible.
I would have left the roast in the oven. Taking it out of the oven most likely had some effect on the cooking time and doneness. Additionally, that could have been dangerous since it would have allowed the roast to sit at an unsafe temperature which could have made the roast a breeding ground for some not so nice things. -Did you cover it the roast with foil when you took it out to keep the heat in?
The time out of the fridge was good.
An instant-read thermometer is a worthwhile and relatively cheap investment. There are "analog" ones as well as some fancy and very fancy digital and electronic models. Or, if you're feeling really ambitious, you could get one of those laser-type ones that are used to check oven temps. The basic "pen-type" should be fine, and they usually run around $10.00. There are a few models out there, and look for one with a dial that will be easiest for you to read. They are also very easy to recalibrate should they get out of whack with a turn of the "nut" on the back of the dial with a wrench.
Just keep in mind that a meat thermometer and an instant-read thermometer are two different creatures. Most meat thermometers are meant to be inserted into the meat for a time while the meat cooks. Instant read thermometers are just that, instant read. Stick the probe in, wait a few seconds, check the temp, take it out.
You can use an instant read thermometer to check the doneness of beef, pork, lamb, chicken, turkey, etc. It also work for checking loaves of bread if your "tap" sense has not been fully finessed. And if you're making a custard or some other egg-based sauces, it's a good way of checking to make sure you've brought the eggs up to a "cooked" temp.
...But a meat thermometer will only run you a few bucks more.
As for being raw near the bone... That's a normal "problem". Sometimes it means the piece of meat was not fully defrosted before being put in the oven - was it frozen before? And sometimes it means that the meat should have stayed in the oven a bit longer. Did you roast your roast bone-down? For pork loin roasts, a rack isn't always necessary since the roast can rest on it's own "chine bone" and serve as it's own rack. This way the heat from the pan goes directly into the bone, helping to cook the roast from the direction.
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Braising!
