To calculate the cash-roll down, we will find the difference between the bond price if six months pass without rates changing or the spread changing and the initial price of the bond and then add this result to the cash carry or the coupon payment.

The cash carry is given by

$$\frac{5}{2} = 2.5$$

The initial price paid for the bond is

$$\frac{2.5}{(1 + 0.02 + 0.0010)^1} + \frac{2.5}{(1 + 0.02 + 0.0010)^2} + \frac{2.5}{(1 + 0.02 + 0.0010)^3} + \frac{102.5}{(1 + 0.02 + 0.0010)^4}$$ $$= \text{USD } 101.52$$

The price of the bond (USD), if six months pass without rates changing or the spread changing, is

$$\frac{2.5}{(1 + 0.02 + 0.0010)^1} + \frac{2.5}{(1 + 0.02 + 0.0010)^2} + \frac{102.5}{(1 + 0.02 + 0.0010)^3} = \text{USD } 101.15$$

Therefore, the carry-roll is 2.13:

$$2.5 + (101.15 - 101.52) = 2.13$$

Alternatively, the carry-roll down can be calculated as

$$(0.02 + 0.0010) \times 101.52 = 2.13$$