Yes it is possible and it not difficult to use. What is difficult is finding out the names of the different modifiers.
Once you know the modifier's name.
The basic command for rolling a check in Roll20 is
/roll 1d20
The easiest way to manage this for a PC that you, the referee control is to create a token and assign it as representing that CHARACTER (not the player, but the character). Select that token and then you can do this.
/roll 1d20+@{selected|str-mod}
You can replace str-mod with the name of anything on the character sheet.
OR
/roll 1d20+@{(character name)|str-mod}
Common Names for 3.5
Attributes
- str-mod
- dex-mod
- con-mod
- int-mod
- wis-mod
- cha-mod
Saves
- fortitude
- reflex
- will
Skills
- appraise
- balance
- bluff
- climb
- concentration
- craft1
- craft2
- craft3
- decipherscript
- diplomacy
- disabledevice
- disguise
- escapeartist
- forgery
- gatherinformation
- handleanimal
- heal
- hide
- intimidate
- jump
- knowarcana
- knowengineer
- knowdungeon
- knowgeography
- knowhistory
- knowlocal
- knownature
- knowability
- knowreligion
- knowplanes
- listen
- movesilent
- openlock
- perform1
- perform2
- perform3
- profession1
- profession2
- profession3
- ride
- search
- sensemotive
- sleightofhand
- spellcraft
- spot
- survival
- swim
- tumble
- usemagicdevice
- userope
- otherskill
How to find out these names for yourself
- Goto the GitHub Roll20 character sheet respository
- Find the character sheet you want and go into it's folder.
- Click on character's sheet html file.
- Click on RAW in the upper right corner of the screen.
Search for the @ symbol. You are looking for macros that will look this.
{{checkroll=[[1d20 + [[@{str-mod}]] ]] }}
In the above str-mod is what you can use in chat. Now the problem in chat is is figuring out which str-mod of which character you want. Which is why you should place a token representing that character and select it. That way you can use the syntax @{target|str-mod} to get the str-mod of that character.