Viola Moonlight
I'm Literally Just Here for WZCW

First sentence starts off in the right direction with description but then you almost give up and give us the short version of where the scene is. We understand that the scene is a prison by you just saying its a prison but to make the start of your RP more interesting, describe the prison room. Describe the condition of the room and what it looks like to set the tone of your RP. You've started things off on a neutral level and the RP then goes off on tangents for the rest of it but I'll get to that point later. Also, you introduced the man as a mysterious person but the next sentence says he is your brother. You could have made it a little more subtle. Something I'd do is:
A man of about forty years old sits behind a lexan window, patiently waiting for someone as he holds a phone in his hand. Moments pass as the man continues to sit there in his chair being watched by the prison guards that keeps the prisoners of the United States Penitentiary from escaping the poorly lit room or causing a riot until another person enters the room from the opposite side of the looking glass. It is Scott Williams, who is directed to his seat near the man where he picks up the phone on the other side.
Man: Hey brother.
Scott: Hey Ross, how you been?
Man: Hey brother.
Scott: Hey Ross, how you been?
It's made the start a little more interesting and if you want to return to this scene in the future, you've already established what the inside looks like to an extent. This makes it easy for readers to follow your RP's should you add other items or features into the room. Description goes a long way.
The dialogue mixed with facial expressions and such I can't make a fault on yet as it is your first RP and we are just starting to get used to Scott Williams. Although your character is listed as "a bit crazy," I feel you've done too much to emphasise something that should only take one or two hints. He laughs and twitches a lot for no reason... I know its what crazy people do but its a bit excessive. You are sounding like our resident crazy man Barbosa almost. Formatting, grammar and spelling looks to be fine which is a great skill to have from the start. Makes people want to read your RP.
Conclusion: Description is half of your RP: don't explain every little single detail but give enough to set the tone, scene, mood, etc. Description can do so much for an RP. Focus on the main parts of your character and you should be right.
P.S. I don't want to seem like a dick here, I'm just giving you the best constructive criticism I can give.