Found this post about using FText::Format on a String Table
In your case, the code (not tested) could be something like this:
int32 Value1 = 1;
int32 Value2 = 2;
int32 Value3 = 3;
FText FormatInput = FText::FromString("{Int1}d{int2} +{int3}"); // 2d6 +3
FFormatNamedArguments Args;
Args.Add("Int1", Value1);
Args.Add("Int2", Value2);
Args.Add("Int3", Value3);
FText FormattedText = FText::Format( FormatInput, Args );