I think the missing values are as follows
C = 100
D = 150500
F = 1
I = 1
L = 150
M = 1410002561
N = 121
Q = 100
R = 1
T = 1
V = 5
W = 55
X = 10
The idea is to determine Roman numerals which form part of the capital letter, list them from left to right (ordered by the leftmost part first and then the rightmost part) and then convert back to decimal.
For example, the left vertical line of the "D" gives an "I" and there is also an "L" contained within it and, of course "D" itself so, from left to right, we have I,L,D which are the numerals for 1,50,500 and so we get 150500 as the value for D.
Letters like "H" are a bit tricky - we take the left vertical line representing "I" first then two vertical lines representing "II" and then the right vertical representing "I" again to get I,II,I or 121.
This caused a little bit of confusion when it came to "M" which contains "I" "II", "M", "IV", "V", "VI" and "I" again but the correct ordering (thanks to OP for explaining) is "I,IV,M,II,V,VI,I" which yields 1410002561
The title (in the brackets) is a conversion of the word ROMAN.
Thanks to Prim3numbah for clearing up my confusion with the letter M.