LOIF

We should be familiar with multiplying two binomials using the FOIL method
(X+4)*(X+5)
First: X*X
Outside: 5*X
Inside: 4*X
Last: 4*5
Answer = X^2 + 9X + 20
In Number Sense, we can do the same when multiplying two 2-digit numbers using a similar method, LOIF.
*Example*
43x27
Last: Multiply the last 2 digits and write down a single digit in the one's place(Carry if necessary)
          3x7 = 21
     Write down the 1 and remember the 2
Outside: Multiply the outside digits but don't write anything else down yet.
          4x7 = 28
     Remember the 28
Inside: Multiply the inside digits and then add to what you got from the outside digits (add any numbers carried from the last digits). Write down a single digit in the ten's place and carry if necessary.
          3x2 = 6
          6+28 = 34
          34+2 = 36
     Write down the 6, carry the 3  
 First: Multiply the first digits and then add any numbers that were carried from the previous step. Write down the number in the hundred's place.
          4x2 = 8
          8+3 = 11
     Write down the 11
Answer = 1161

The 11 Trick!

The 11 Trick is one of the easiest tricks out there, but it can be INCREDIBLY useful on the number sense test. When multiplying any number greater than 10 by 11, there's a very easy process to do that gets you the right answer with practically no effort. For example:

65 x 11

The number in the units place of the answer will be 5. For the middle number, add 6 and 5 together, to get 11. Place a 1 in the tens place of the answer and carry the one over to the 6, which becomes a 7, for the hundreds place.

To make it more simple, when multiplying 11 by the number A'B, you will end up with answer A'A+B'B. This works with longer numbers as well - simply continue adding the middle two numbers, starting from the right, and carry over the remainders. Here are some other examples:

43 x 11 = 473
89 x 11 = 979
129 x 11 = 1419
462 x 11 = 5082

This might help in giving you a clearer picture on how the questions on the test are spread out. I personally would only focus on 1-20 until you master it, then move on to the rest.
http://www.uiltexas.org/files/academics/number-sense-sequencing.pdf

Roman Numerals

First off what are Roman Numerals and why are they still relevant?
  Roman Numerals were the symbols that utilized letters from the Roman alphabet, collectively known as an ancient numerical system used in Ancient Rome. Today we use Roman Numerals for copyright credits at the end of films, organization of outlines (i) (ii) (iii) (iv), numbering Super Bowls, names of Monarchs and royalty.

What are our Roman Numerals?
  I=1
  V=5
  X=10
  L=50
  C=100
  D=500
  M=1,000
 

 The following were introduced later to represent larger, more complex numbers. They should be represented with a Bar over their tops. These however are highly unlikely to be on any Number Sense tests.

*V=5,000
*X=10,000
*L=50,000
*C=100,000
*D=500,000
*M=1,000,000