As mentioned before you will need to have some direct conversations with your roommate / best friend. This might be awkward or strange but you can get through it and no matter what the outcome it will be better in the long run. When having these conversations start with saying "this might be awkward or weird", since acknowledging this will remove most of the awkwardness.
First off you need to talk with them about wanting to try to date. Specify that you want them to stay living with you but there might be changes around the house and that you might be bringing people over when its that time. Be upfront about it and let them know. If you are both on the same page about not being in a "relationship" this should not be a problem. (Note: even friendship is a relationship so you two have a relationship just not a boyfriend/girlfriend romantic relationship). Lead with everything you said here "wouldn’t want to sacrifice our relationship just so I can start dating again." is a great start.
When dating make sure to bring up this situation early and as a positive thing, since for the right person this is a huge green flag. In the first few dates when talking about your living situation mention you live with a person who you dated and hooked up with a few time but the romance fizzled and now you are close friends. This should be positive to show you treat your potential sexual/romantic partners as people not objects and will be a good way to weed out people who are too jealous of your situation. If someone doesn't want to see you after this disclosure you don't want to be with that person. Make sure any potential dates gets to meet your roommate early to see you can interact with opposite gender people as friends. (Note: I am assuming you are mixed genders since this is a complete non-issue in queer spaces). Hiding your roommate / best friend won't help anyone.
As you get to know your dates longer once you get to the "relationship" and monogamy opt-in moment (3 to 6 months in) make sure you have an explicit conversation about it. What does this mean for you and them and what is and isn't allowed. This might mean no more sexual situations with your roommate / best friend but might not. Same with cuddling and snuggling with your roommate / best friend. At this point any new "boyfriend / girlfriend" and roommate / best friend should know each other and can judge what that means to them.
This slightly more complicated to everyone else but not by much. Your situation isn't anything crazy and shouldn't be a deal breaker. Just talk about it. You got this!!!!
This really isn't that complex except it doesn't fit the standard dominant heteronormative story for dating. Those stories where your eyes met across the bar and you fall in love with your new partner instantly. You either then stay together forever in the "success" story or fall apart in a dramatic fashion and never see each other again for a "failure" story. This isn't common and real life is more messy for these "failures". Just note that most people leave out the mess when telling their romantic "success" stories. I dated / hooked up with lots of my wives friends before we are started dating and so did she.
You had your best friend / roommate were / are a "failure" in this model but a success in real life. You made a real friendship out of failed dates and romantic relationship. That's a success.
Just be upfront and honest with everyone. Make sure your roommate / best friend agrees that you don't have a romantic future but rather what you currently have. Tell your future dates a simplified story about your roommate upfront and everyone will be cool. You got this