Since we have no idea what your skill level is it's hard to say.
Looks like someone cover over some rotten wood instead of fixing it.
The sheathing at the bottom of the roof also looks funky.
I'd remove some shingles in that area to see just how bad it is.
If it's bad then your going to just need to replace it with a new sheet of OSB.
That rake board could have been installed to close to the other roof and it wicked up moisture, or someone installed the metal from the top down instead of from the bottom up so water can get in behind it.
Could be as simple as remove all the rotten wood and replacing it.
You going to have to get someone to bend you a new piece of coil stock to go back over the new wood. Any siding company can bend you on in a few min.
Should only need some simple tools, hammer, nails, flat bar, ciruler saw.
Looks like no one installed drip cap on the outside edges of the roof sheathing. That can allow water to be able to get into the sheathing.
Clean out those gutters while you up there. While your working in that area check for wood rot down near the gutters. Looks like the roof is sagging in that area.
Last edited by joecaption; 02-25-2012 at 02:46 PM.