The Document Raster Effects Settings are stored in the root of the Document Dictionary under the key "AI Auto Rasterize". I have a feeling that the key might not exist if the raster effects settings have not been set - I might be wrong on this though. However it's worth bearing this in mind when you attempt to obtain them and code around that scenario accordingly, i.e. check for a null dictionary reference when you attempt to get the Rasterize dictionary etc.
Please note that I've just written this from memory - there's no error checking and there might be typo's etc.
#include "IAIRef.h"
...
ai::Ref<AIDictionaryRef> docDict;
ai::Ref<AIDictionaryRef> rastDict;
sAIDocument->GetDictionary(docDict << ai::Replace);
sAIDictionary->GetDictEntry(docDict, sAIDictionary->Key("AI Auto Rasterize"), rastDict << ai::Replace);
AIReal padd; // Padding around object in points (I think)
AIBoolean spot; // Preserve Spot Colours True/False
AIBoolean mask; // Create Clipping Mask True/False
ai::int32 dpi; // Resolution as an integer
AIBoolean alis; // Anti-Alias True/False
ai::int32 colr; // Color Model - This value determines both Color Model and Background. It might be a bit-field but I can't remember right now. Have a play with the values in the dialog and see what you get back
sAIDictionary->GetRealEntry(rastDict, sAIDictionary->Key("padd"), &padd);
sAIDictionary->GetBooleanEntry(rastDict, sAIDictionary->Key("spot"), &spot);
sAIDictionary->GetBooleanEntry(rastDict, sAIDictionary->Key("mask"), &mask);
sAIDictionary->GetIntegerEntry(rastDict, sAIDictionary->Key("dpi."), &dpi;
sAIDictionary->GetBooleanEntry(rastDict, sAIDictionary->Key("alis"), &alis);
sAIDictionary->GetIntegerEntry(rastDict, sAIDictionary->Key("colr"), &colr);
I hope this helps.
-W